playlist: Simplify playlist_load
Reset fd for the on-disk playlist at the place where
ownership is transferred in playlist_set_current (which
already has a note, that the playlist will be effectively
closed, but did not reset the fd).
Also ensure, that calling playlist_load closes the fd for
the on-disk playlist (and its control file), if any were
left open - even though this is not supposed to happen.
Generate name of control file in playlist_init to be more
consistent with the behavior for the current playlist.
Only a single playlist can be loaded in the playlist viewer
at the same time, so generating random names shouldn't be
needed.
Change-Id: I65e0fc07ce608c1d333a90447e18482787a98b8c