test: execute other tests in a new session

The main reason is to execute tests without a control termnal and avoid
a case when tests try to use the --shell-job options.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/Makefile

@@ -18,7 +18,7 @@ TESTS = unix-callback mem-snap rpc libcriu mounts/ext security pipes crit socket
 
 other: .FORCE
 	for t in $(TESTS); do				\
-		$(MAKE) -C $$t run || exit 1;	\
+		setsid $(MAKE) -C $$t run || exit 1;	\
 	done						\
 
 zdtm-tst-list: zdtm.sh