Change from lazy media storage cleanup to eager

Before, if there was any storage location below max use threshold, the
cleanup was skipped. This might cause problem described in
#656 :
as long as one location has space, others might fill up if used by other
processes. The default location, /var/lib/bluecherry/recordings/ is
usually on the system rootfs, where many services' and users' activities
contribute to increasing the filesystem space used.

Now, the media cleanup happens if any of the storage locations is over
the threshold.

server/bc-server.cpp

@@ -1189,12 +1189,12 @@ static int bc_cleanup_media()
 static int bc_check_media(void)
 {
 	int ret = 0;
-	bool storage_overloaded = true;
+	bool storage_overloaded = false;
 
 	/* If there's some space left, skip cleanup */
 	for (int i = 0; i < MAX_STOR_LOCS && media_stor[i].max_thresh; i++) {
-		if (is_storage_full(&media_stor[i]) != 1) {
-			storage_overloaded = false;
+		if (is_storage_full(&media_stor[i]) == 1) {
+			storage_overloaded = true;
 			break;
 		}
 	}