libzrtp: fix client-side enrollment

It appears that libzrtp would prevent a non-passive client from
enrolling with a PBX because of a broken license mode comparison.

Thanks to Ivo Kutts for the report.

FS-4223 --resolve

libs/libzrtp/src/zrtp_pbx.c

@@ -356,7 +356,7 @@ zrtp_status_t zrtp_register_with_trusted_mitm(zrtp_stream_t* stream)
 	
 	/* Passive Client endpoint should NOT generate PBX Secret. */
 	if ((stream->mitm_mode == ZRTP_MITM_MODE_REG_CLIENT) &&
-		(ZRTP_LICENSE_MODE_PASSIVE != stream->zrtp->lic_mode)) {
+		(ZRTP_LICENSE_MODE_PASSIVE == stream->zrtp->lic_mode)) {
 		ZRTP_LOG(2,(_ZTU_,"WARNING: Passive Client endpoint should NOT generate PBX Secert.\n"));
 		return zrtp_status_bad_param;
 	}