Don't even attempt to unload libqstart_gtklo.so again

...for no apparent gain.  IdleUnloader introduced in
a8b42ddd66bba4b6f26a4d2d793051752989938e "Fix i#101245#" was probably a
misguided reaction to osl::Module's dtor starting to call dlclose back then.

(cherry picked from commit 73aaa3cf5e18d008268f4b67bbb60070b2cafc6a)
Conflicts:
        sfx2/source/appl/shutdownicon.cxx
        sfx2/source/appl/shutdowniconunx.cxx

Change-Id: I9a5e99d8cfba13e3750331597d64f58135537e9b
Reviewed-on: https://gerrit.libreoffice.org/11851
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>