Fix (and support) nxos VXLAN nve interfaces (#2195)

Author: mjbear

ntc_templates/templates/cisco_nxos_show_interface.textfsm

@@ -67,7 +67,7 @@ Start
   ^\s+Internet\s+Address\s+is\s+${IP_ADDRESS}\/${PREFIX_LENGTH}
   ^\s+Port\s+mode\s+is\s+${MODE}
   ^\s+${DUPLEX},\s+${SPEED}(,\s+media\s+type\s+is\s+${MEDIA_TYPE})?\s*$$
-  ^\s+MTU\s+${MTU}.*BW\s+${BANDWIDTH}.*DLY\s+${DELAY}
+  ^\s+MTU\s+${MTU}(.*BW\s+${BANDWIDTH}.*DLY\s+${DELAY})?
   ^\s+Encapsulation\s+${ENCAPSULATION},?(\s+Virtual\s+LAN,\s+Vlan\s+ID\s+${VLAN_ID},)?
   ^\s+${INPUT_PACKETS}\s+input\s+packets\s+\d+\s+bytes\s*$$
   ^\s+${OUTPUT_PACKETS}\s+output\s+packets\s+\d+\s+bytes\s*$$

tests/cisco_nxos/show_interface/cisco_nxos_show_interface11_nve.raw

@@ -0,0 +1,6 @@
+nve1 is up
+admin state is up,  Hardware: NVE
+  MTU 9216 bytes
+  Encapsulation VXLAN
+  Auto-mdix is turned off
+  RX

tests/cisco_nxos/show_interface/cisco_nxos_show_interface11_nve.yml

@@ -0,0 +1,56 @@
+---
+parsed_sample:
+  - admin_state: "up"
+    babble: ""
+    bad_etype_drop: ""
+    bad_proto_drop: ""
+    bandwidth: ""
+    bandwidth_input_rate: ""
+    bandwidth_output_rate: ""
+    bia: ""
+    collisions: ""
+    crc: ""
+    deferred: ""
+    delay: ""
+    description: ""
+    dribble: ""
+    duplex: ""
+    encapsulation: "VXLAN"
+    giants: ""
+    hardware_type: ""
+    ignored: ""
+    input_discards: ""
+    input_errors: ""
+    input_packets: ""
+    interface: "nve1"
+    interface_down_drop: ""
+    ip_address: ""
+    last_link_flapped: ""
+    late_collisions: ""
+    link_status: "up"
+    lost_carrier: ""
+    mac_address: ""
+    media_type: ""
+    mode: ""
+    mtu: "9216"
+    no_buffer: ""
+    no_carrier: ""
+    output_discards: ""
+    output_errors: ""
+    output_packets: ""
+    overrun: ""
+    packet_input_rate: ""
+    packet_output_rate: ""
+    prefix_length: ""
+    runts: ""
+    rx_jumbo_packets: ""
+    rx_pause: ""
+    short_frame: ""
+    speed: ""
+    stomped_crc: ""
+    storm_suppression_bytes: ""
+    tx_jumbo_packets: ""
+    tx_pause: ""
+    underrun: ""
+    vlan_id: ""
+    watchdog: ""