Gallery: fix a memory leak

The requestAudioFocus() call does not provide the listener previously
registered, so it remains in AudioManager and eventually leaks
MovieActivity.

The regression is introduced by
Id8e3e4b0afbc72892301a08fb8a122c285fbfe97.

Change-Id: I032cfb9df1973420a51476bba139294badee1366
CRs-Fixed: 999702
3 files changed