copy the CCACHE bit on clones of devmnt chans.

Reference: /n/sources/patch/applied/ccache-flag
Date: Mon Apr 29 17:38:50 CES 2013
Signed-off-by: nemo@lsub.org

--- /sys/src/9/port/devmnt.c	Mon Apr 29 17:37:04 2013
+++ /sys/src/9/port/devmnt.c	Mon Apr 29 17:36:48 2013
@@ -412,6 +412,7 @@
 		alloc = 1;
 	}
 	wq->clone = nc;
+	nc->flag |= c->flag&CCACHE;
 
 	if(waserror()) {
 		mntfree(r);