use_blanket

Add ... blanket=/dev ... for mount_ffs to satisfy realpath.

diff -r 25cedfb0c725 -r cd55caa42bc6 tests/fs/nfs/t_rquotad.sh
--- tests/fs/nfs/t_rquotad.sh
+++ tests/fs/nfs/t_rquotad.sh
@@ -110,7 +110,8 @@ get_nfs_quota()
 	/bin/echo "/export -noresvport -noresvmnt 10.1.1.100" | \
 		dd of=/rump/etc/exports 2> /dev/null
 
-	atf_check -s exit:0 -e ignore mount_ffs /dk /rump/export
+	atf_check -s exit:0 -e ignore env RUMPHIJACK='path=/rump,blanket=/dk' \
+		mount_ffs /dk /rump/export
 
 #set a quota limit (and check that we can read it back)
 	for q in ${expect} ; do
diff -r 25cedfb0c725 -r cd55caa42bc6 tests/lib/librumphijack/t_tcpip.sh
--- tests/lib/librumphijack/t_tcpip.sh
+++ tests/lib/librumphijack/t_tcpip.sh
@@ -182,7 +182,8 @@ test_nfs()
 
 	atf_check -s exit:0 rump.sysctl -q -w kern.module.autoload=1
 
-	atf_check -s exit:0 -e ignore mount_ffs /dk /rump/export
+	atf_check -s exit:0 -e ignore env RUMPHIJACK='path=/rump,blanket=/dk' \
+		mount_ffs /dk /rump/export
 	atf_check -s exit:0 -x "echo ${magicstr} > /rump/export/im_alive"
 
 	# start rpcbind.  we want /var/run/rpcbind.sock
diff -r 25cedfb0c725 -r cd55caa42bc6 tests/lib/librumphijack/t_vfs.sh
--- tests/lib/librumphijack/t_vfs.sh
+++ tests/lib/librumphijack/t_vfs.sh
@@ -35,7 +35,8 @@ domount()
 
 	mntdir=$1
 	[ $# -eq 0 ] && mntdir=/rump/mnt
-	atf_check -s exit:0 -e ignore mount_ffs /img ${mntdir}
+	atf_check -s exit:0 -e ignore env RUMPHIJACK='path=/rump,blanket=/img' \
+		mount_ffs /img ${mntdir}
 }
 
 dounmount()