Update cisco_ios_ping.textfsm (networktocode#1563)

* Update cisco_ios_ping.textfsm

Added U and Q response to RESPONSE STREAM

Cisco has for valid outputs for ping: .(fail) ! (success) U (unreachable) Q (quench)

U and Q where missing. Testing an output that carried these values would generate an error.

ntc_templates/templates/cisco_ios_ping.textfsm

@@ -3,7 +3,7 @@ Value Required SENT_TYPE (.*)
 Value Required DESTINATION (\S+)
 Value Required TIMEOUT (\d+)
 Value SOURCE (\S+)
-Value List RESPONSE_STREAM ([\.\!]+)
+Value List RESPONSE_STREAM ([\.\!/U/Q]+)
 Value Required SUCCESS_PCT (\d+)
 Value Required SUCCESS_QTY (\d+)
 Value RTT_MIN (\d+)