Apply blocking policy in ALCpulsePlayback_open() function

Apply blocking policy in ALCpulsePlayback_open() function

If application uses media session with MIX_WITH_OTHERS option and other process
has already acquired a focus which has more higher priority than media, an error
will be returned from this function.

[Version] Release 1.17.2-7
[Profile] Common
[Issue Type] Backward compatibility

Change-Id: Idd83c1dbf24215fd33d3fb432ebaa3b101df756c
Signed-off-by: Sangchul Lee <sc11.lee@samsung.com>
(cherry picked from commit 9ea79405d067810bedbd76fe9492d236d4576d52)