Remove unnecessary variables for controlling thread

Remove unnecessary variables for controlling thread

- Issue:
When PlayerThread is destructing, main thread can be in deadlock.

- Solution:
This patch removes unnecessary condition variable and mutex for thread.
The root cause of the deadlock is because of the wrong usage of two
different mutex for controlling single thread. This patch simplifies the
thread function and thread controlling logic using timed_mutex and
condition_variable_any. Through this change, the PlayerThread instance
can clear the reserved thread more quickly.

Change-Id: I8fa79f7c4e25595641fc651394e550d545360f75
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>