Fix 3 line output for nxos ShowBgpVrfAllAllSummary

[mattchilders]

On NXOS if the IPv6 address is too long it will cause the other values to wrap to a new line. If the AS on the second line is too long (in the case of a 4-byte ASN) it will wrap to a third line. Like below:

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down...
2001:db8:c006:ff:251::1
4 406942
0 0 0 0 0 05:49:52 Idle

Currently the parser will error out on 3-line cases, and this change adds a fix to parse them correctly. The fix adds a p8_2_1 regex that matches the 2nd line. In 3-line case, p8_1 will match the neighbor, the newly added p8_2_1 will match the version and AS, and the existing p8_4 will match the remaining values.

Description

Motivation and Context

This changes fixes a bug with BGP 3-line outputs on NXOS

Impact (If any)

None that I'm aware of

Screenshots:

Checklist:

• [ x ] I have updated the changelog.
• I have updated the documentation (If applicable).
• [ x ] I have added tests to cover my changes (If applicable).
• [ x ] All new and existing tests passed.
• All new code passed compilation.