e_mod_rotation_wl: add exception handle for rotation done ack

e_mod_rotation_wl: add exception handle for rotation done ack

Rotation change event flows like below
   Server -> Client [PID:3564] tizen_rotation@39.angle_change with angle,serial
   Server <- Client [PID:3564] tizen_rotation@39.ack_angle_change with serial
BTW, issue happened once a client acks rotation_done ahead of event from server
serial number is initialized 0,and plus on every angle change event.
if arrival ack from client contains serial "0", it is not valid number.

Change-Id: I57d0eed5d109718df969c6bdbd7ba886cc01ce79