Adding port_admin_state_change option to config

Adding the ability to skip test_update_instance_port_admin_state
when this operation is not supported by the test environment.
Closes-Bug: 1436839

Change-Id: Icda251c46e2fefcc80b0c712d6f42d76a7d247b7
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 175f0d9..9007e51 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -796,6 +796,10 @@
 # attributes ipv6_ra_mode and ipv6_address_mode (boolean value)
 #ipv6_subnet_attributes = false
 
+# Does the test environment support changing port admin state (boolean
+# value)
+#port_admin_state_change = true
+
 
 [object-storage]