app_chanspy.c: resolving the issue writing frame to whisper audiohook.

app_chanspy.c: resolving the issue writing frame to whisper audiohook.

ChanSpy(${channel}, qEoSw): because flags set o, ast_audiohook_set_frame_feed_direction(audiohook, AST_AUDIOHOOK_DIRECTION_READ); this will effect whisper audiohook and spy audiohook, this makes writing frame to whisper audiohook impossible. So add function start_whispering to starting whisper audiohook.

Resolves: #876
(cherry picked from commit 03983b2ff9af730fb00141b27f9986c4a54d427c)