Take the lock when reading as well as writing the third part dynamic FS module list while ensuring that the known Subversion modules continue to be accessed without locking.
Take the lock when reading as well as writing the third part dynamic
FS module list while ensuring that the known Subversion modules continue
to be accessed without locking.

* subversion/libsvn_fs/fs-loader.c
  (get_or_allocate_third): Start loop at point determined by caller,
   return early if the module is found.
  (get_library_vtable): Check the known Subversion modules outside
   the lock, move the rest of the loop inside the lock.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1369081 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion