zdtm: zdtm.py: reset $PATH to canonical in ns tests

This is to deal with distros like Arch which take /usr merge to the
extreme and set their $PATH to something like /usr/local/bin:/usr/bin
(no /usr/sbin, no /{s,}bin), which breaks our rather inflexible nsroot
population logic.
Signed-off-by: Ivan Shapovalov <intelfx@intelfx.name>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm.py

@@ -344,6 +344,7 @@ class zdtm_test:
 		if self.__flavor.ns:
 			env['ZDTM_NEWNS'] = "1"
 			env['ZDTM_ROOT'] = self.__flavor.root
+			env['PATH'] = "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 
 			if self.__flavor.uns:
 				env['ZDTM_USERNS'] = "1"