tests: fix test_play_media_info failure and re-enable player tests

Submitted by Edward Hervey @bilboed

Link to original bug (#787374)

Description

Created attachment 359283
GST_DEBUG Log of failure

libs/player.c:753:F:general:test_play_media_info:0: 'GPOINTER_TO_INT (state.test_data)' (2) is not equal to '1' (1)

The "problem" is that more than one media info update gets emitted (because some information gets updated after a while, like bitrates).

Attachment 359283, "GST_DEBUG Log of failure":
log

Depends on: #394 (closed).