tftp: Close a resource leak when putting files

Reported by:	Coverity
CID:		1394842
MFC after:	2 weeks

usr.bin/tftp/main.c

@@ -499,6 +499,7 @@ put(int argc, char *argv[])
 			printf("putting %s to %s:%s [%s]\n",
 			    cp, hostname, targ, mode);
 		xmitfile(peer, port, fd, targ, mode);
+		close(fd);
 		return;
 	}
 				/* this assumes the target is a directory */