Fix log channel initialization at bionic/logd_write.c.

log_channel_t contains fd member, which is file descriptor for
exact logging channel. change cc05d1271680d6a7804bc89d3b1fe14c40b32396
lacks initialization of this member in __write_to_log_init(), thus
logging code is not working, although not crashable.

Additional details may be found in comments here:
http://review.source.android.com/5617

libc/bionic/logd_write.c

@@ -113,6 +113,8 @@ static int __write_to_log_init(log_id_t log_id, struct iovec *vec)
         log_channels[log_id].logger =
             (fd < 0) ? __write_to_log_null : __write_to_log_kernel;
 
+        log_channels[log_id].fd = fd;
+
         pthread_mutex_unlock(&log_init_lock);
 
         return log_channels[log_id].logger(log_id, vec);