touch should just try to set the mtime, if the file server
will let it. try this change and see if it behaves better.

%% diff -n touch.c  /sys/src/cmd/touch.c
touch.c:30 c /sys/src/cmd/touch.c:30
< 	Dir stbuff, nstbuff;
---
> 	Dir stbuff;
touch.c:39,44 d /sys/src/cmd/touch.c:38
< 	}
< 	stbuff.mtime = time(0);
< 	if(dirwstat(name, &stbuff) >= 0){
< 		/* check that file server paid attention */
< 		if(dirstat(name, &nstbuff) >=0 && nstbuff.mtime == stbuff.mtime)
< 			return 0;
%%