Running =(org-babel-tangle)= from inside a =src= block ignores
=header-args= properties
Consider the following org-mode file set for tangling.
This code should run the command =org-babel-tangle= #+BEGIN_SRC
emacs-lisp  :results silent
(org-babel-tangle)
#+END_SRC
that should tangle the stuff in the next header.

** Observed behaviour
Running the first code block tangles only the first code block below
Running =org-babel-tangle= tangles both code blocks below


** Expected behaviour
Running the above code block or =org-babel-tangle= tangles both code
blocks below


* Code to tangle
** Because of =:tangle= parameter
This block gets tangled both by executing =org-babel-tangle= from the
=src= code block or directly via M-x.

  #+BEGIN_SRC emacs-lisp :tangle yes
  (message "This should be tangled because of :tangle parameter")
  #+END_SRC



** Because of properties
  :PROPERTIES:
  :header-args:  :tangle yes   :END:

This block gets tangled only by executing =org-babel-tangle=  directly
via M-x but it *doesn't* get tangled by executing =org-babel-tangle=
from the =src= code block.

  #+BEGIN_SRC emacs-lisp
  (message "This should be tangled because of property list")
  #+END_SRC



--------------------------

Emacs  : GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-05-29
Package: Org mode version 9.1.9 (release_9.1.9-65-g5e4542 @
/usr/share/emacs/26.1/lisp/org/)

current state:
==============
(setq
 org-src-mode-hook '(org-src-babel-configure-edit-buffer
		     org-src-mode-configure-edit-buffer)
 org-after-todo-state-change-hook '(org-clock-out-if-current)
 org-metadown-hook '(org-babel-pop-to-session-maybe)
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 org-mode-hook '(#[0 "\300\301\302\303\304$\207"
		   [add-hook change-major-mode-hook org-show-block-all append
		    local]
		   5]
		 #[0 "\300\301\302\303\304$\207"
		   [add-hook change-major-mode-hook org-babel-show-result-all
		    append local]
		   5]
		 org-babel-result-hide-spec org-babel-hide-all-hashes)
 org-archive-hook '(org-attach-archive-delete-maybe)
 org-confirm-elisp-link-function 'yes-or-no-p
 org-agenda-before-write-hook '(org-agenda-add-entry-text)
 org-metaup-hook '(org-babel-load-in-session-maybe)
 org-bibtex-headline-format-function #[257 "\300\236A\207" [:title] 3
"\n\n(fn ENTRY)"]
 org-babel-pre-tangle-hook '(save-buffer)
 org-tab-first-hook '(org-babel-hide-result-toggle-maybe
		      org-babel-header-arg-expand)
 org-occur-hook '(org-first-headline-recenter)
 org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-hide-drawers
		  org-cycle-show-empty-lines
		  org-optimize-window-after-visibility-change)
 org-speed-command-hook '(org-speed-command-activate
			  org-babel-speed-command-activate)
 org-confirm-shell-link-function 'yes-or-no-p
 org-link-parameters '(("id" :follow org-id-open)
		       ("rmail" :follow org-rmail-open :store
			org-rmail-store-link)
		       ("mhe" :follow org-mhe-open :store org-mhe-store-link)
		       ("irc" :follow org-irc-visit :store org-irc-store-link)
		       ("info" :follow org-info-open :export org-info-export
			:store org-info-store-link)
		       ("gnus" :follow org-gnus-open :store
			org-gnus-store-link)
		       ("docview" :follow org-docview-open :export
			org-docview-export :store org-docview-store-link)
		       ("bibtex" :follow org-bibtex-open :store
			org-bibtex-store-link)
		       ("bbdb" :follow org-bbdb-open :export org-bbdb-export
			:complete org-bbdb-complete-link :store
			org-bbdb-store-link)
		       ("w3m" :store org-w3m-store-link) ("file+sys")
		       ("file+emacs") ("doi" :follow org--open-doi-link)
		       ("elisp" :follow org--open-elisp-link)
		       ("file" :complete org-file-complete-link)
		       ("ftp" :follow
			(lambda (path) (browse-url (concat "ftp:" path))))
		       ("help" :follow org--open-help-link)
		       ("http" :follow
			(lambda (path) (browse-url (concat "http:" path))))
		       ("https" :follow
			(lambda (path) (browse-url (concat "https:" path))))
		       ("mailto" :follow
			(lambda (path) (browse-url (concat "mailto:" path))))
		       ("news" :follow
			(lambda (path) (browse-url (concat "news:" path))))
		       ("shell" :follow org--open-shell-link))
 )