Change sequential searching algoritmh to return 503 response if it was last received response in target search process
Change sequential searching algoritmh to return 503 response if it was last received response in
target search process

issue #503

Signed-off-by: Kirill Mikhailov <0f3f7051f127a7dd3500665f861cf9004c9d4d2f@gmail.com>

voxology/sip-server,kirm/sip.js,newpouy/sip.js