Fix cisco n1kv plugin cli option and help

Rename VXLAN option to OVERLAY and add help for sub-type field in
the Cisco N1kv specific cli to accomodate
cisco-plugin-n1k-enh-vxlan-support blueprint.

Change-Id: I4a3dc7ad1b45f6effebd6fd337c51e7c0eeba84c
Closes-Bug: #1220966

Author: abhiraut

neutronclient/neutron/v2_0/networkprofile.py

@@ -23,8 +23,7 @@
 from neutronclient.openstack.common.gettextutils import _
 
 RESOURCE = 'network_profile'
-SEGMENT_TYPE_CHOICES = ['vlan', 'vxlan', 'multi-segment', 'trunk']
-SEGMENT_SUBTYPE_CHOICES = ['vlan', 'vxlan']
+SEGMENT_TYPE_CHOICES = ['vlan', 'overlay', 'multi-segment', 'trunk']
 
 
 class ListNetworkProfile(neutronV20.ListCommand):
@@ -58,9 +57,11 @@ def add_known_arguments(self, parser):
         parser.add_argument('segment_type',
                             choices=SEGMENT_TYPE_CHOICES,
                             help='Segment type')
+        # TODO(Abhishek): Check on sub-type choices depending on segment_type
         parser.add_argument('--sub_type',
-                            choices=SEGMENT_SUBTYPE_CHOICES,
-                            help='Sub-type for the Segment')
+                            help='Sub-type for the segment. Available sub-'
+                            'types for overlay segments: native, enhanced; '
+                            'For trunk segments: vlan, overlay.')
         parser.add_argument('--segment_range',
                             help='Range for the Segment')
         parser.add_argument('--physical_network',