qrexec: prefer VM-local service file (if present) over default one

This will allow a service to be overridden per-VM.

qrexec/qubes-rpc-multiplexer

@@ -14,7 +14,7 @@ if ! [ $# = 2 ] ; then
 fi
 export QREXEC_REMOTE_DOMAIN="$2"
 
-for CFG_FILE in $QUBES_RPC/"$1" $LOCAL_QUBES_RPC/"$1"; do
+for CFG_FILE in $LOCAL_QUBES_RPC/"$1" $QUBES_RPC/"$1"; do
 	if [ -s "$CFG_FILE" ]; then
         break
 	fi