Tempest: Edited bash commands to work with multiple OSes.

Edited the "CONFIGURE_VLAN_INTERFACE_COMMANDS" with PATH
configration that will allow rhel "cloud-user" to pass
commands via ssh.

The cause for that fix is that pre-fix approach works with
rhel root but not rhel non root.

Change-Id: I73f0f79ac6b34a1a5b1b22406f730dfd1266d5d5
diff --git a/neutron/tests/tempest/scenario/test_trunk.py b/neutron/tests/tempest/scenario/test_trunk.py
index 54399aa..f687b59 100644
--- a/neutron/tests/tempest/scenario/test_trunk.py
+++ b/neutron/tests/tempest/scenario/test_trunk.py
@@ -27,9 +27,10 @@
 CONF = config.CONF
 
 CONFIGURE_VLAN_INTERFACE_COMMANDS = (
-    'IFACE=$(ip l | grep "^[0-9]*: e" | cut -d \: -f 2) && '
+    'IFACE=$(PATH=$PATH:/usr/sbin ip l | grep "^[0-9]*: e" |'
+    'cut -d \: -f 2) && '
     'sudo su -c '
-    '"ip l a link $IFACE name $IFACE.%(tag)d type vlan id %(tag)d && '
+    '"ip l a link $IFACE name $IFACE.%(tag)d type vlan id %(tag)d &&'
     'ip l s up dev $IFACE.%(tag)d && '
     'dhclient $IFACE.%(tag)d"')