Should fix #2142

This fix partially #2142

(and add ftp and smb to the list)

Basically this test was expecting that /tmp is a directory. On Mac OS X /tmp is a link to /private/tmp.

We work around by getting the current work directory after chdir.

 It fixed a segfault when using hotkeys for the OSD.
 I am not sure it is perfectly fine, but var_AcquireMutex seems
to have been removed without a proper replacement.

Should we keep this code?

This should fix the compilation of pda interface.