qrexec: adjust for new qrexec-policy

New qrexec-policy can provide information about original target domain,
even if later overriden by policy (using target= keyword).

qrexec/qubes-rpc-multiplexer

@@ -8,10 +8,11 @@ rm -f /tmp/qrexec-rpc-stderr.$$
 QUBES_RPC=/etc/qubes-rpc
 LOCAL_QUBES_RPC=/usr/local/etc/qubes-rpc
 
-if ! [ $# = 2 ] ; then
-	echo $0: bad argument count, usage: $0 SERVICE-NAME REMOTE-DOMAIN-NAME >&2
+if ! [ $# = 2 -o $# == 3 ] ; then
+	echo "$0: bad argument count, usage: $0 SERVICE-NAME REMOTE-DOMAIN-NAME [REQUESTED_TARGET]" >&2
 	exit 1
 fi
+export QREXEC_REQUESTED_TARGET="$3"
 export QREXEC_REMOTE_DOMAIN="$2"
 export QREXEC_SERVICE_FULL_NAME="$1"
 SERVICE_WITHOUT_ARGUMENT="${1%%+*}"