Safeguard cancellation zone for IO threads

Thread cancellation is allowed only in the safety zone - poll and read
after the poll. It is easier to maintain strictly defined place for such
a potentially destructive functionality - resources can not be allocated
in such a zone. So, we have to make sure, that if we jump off this zone
by the usage of break or goto statement, the code which follows will not
be canceled - resources can be safely released.

src/io.c

@@ -407,6 +407,7 @@ void *io_thread_a2dp_sink_sbc(void *arg) {
 	}
 
 fail:
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 	pthread_cleanup_pop(1);
 	pthread_cleanup_pop(1);
 	pthread_cleanup_pop(1);
@@ -599,6 +600,7 @@ void *io_thread_a2dp_source_sbc(void *arg) {
 	}
 
 fail:
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 	pthread_cleanup_pop(1);
 	pthread_cleanup_pop(1);
 	pthread_cleanup_pop(1);
@@ -741,6 +743,7 @@ void *io_thread_a2dp_sink_aac(void *arg) {
 	}
 
 fail:
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 	pthread_cleanup_pop(1);
 	pthread_cleanup_pop(1);
 fail_init:
@@ -1023,6 +1026,7 @@ void *io_thread_a2dp_source_aac(void *arg) {
 	}
 
 fail:
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 	pthread_cleanup_pop(1);
 	pthread_cleanup_pop(1);
 fail_init:
@@ -1168,6 +1172,7 @@ void *io_thread_rfcomm(void *arg) {
 	}
 
 fail:
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 	pthread_cleanup_pop(1);
 	return NULL;
 }