audio-io fixed crash at audio_in_read() of another thread.

audio-io fixed crash at audio_in_read() of another thread.

There are no syncronization between audio_in_read() and audio_in_unprepare().
Therefore, assert crash occurs possibly while use multiple reader thread.

Changes:
 * Add locking method at audio_in_read() and null check of mpPulseAudioClient.
 * Fixed syncronous-method of audio_out_write() too.
 * Miscellaneous typos are fixed.

[Version] 0.3.45
[Profile] Common
[Issue Type] Bug Fix

Signed-off-by: KimJeongYeon <jeongyeon.kim@samsung.com>
Change-Id: I18147b9e1e7bb5c16816250d65d2ff066f6383b7