org-edit-src-code doesn't seem to be unescaping correctly.  For
example, calling org-edit-src-code on

#+begin_src org
  ,* h
#+end_src

puts ",* h", not "* h", in the source buffer.  When exiting, ",*" is
escaped again, resulting in

#+begin_src org
  ,,* h
#+end_src

The attached patch moves the unescaping call from org-edit-src-code to
org-src--edit-element so that the source string is unescaped
regardless of whether it was passed as an argument or extracted
directly from the buffer.