BGP: Add a test capture file

This capture file triggered a buffer over-read with the 4.9.2 release
fixed in the 4.9.3 release.

With a length check previously added, the problem no longer exists.
Thus no fix needed.

The pcap file was updated to pass the sanity checks and to avoid
pcap_loop() error messages.

Update the output of the test accordingly.

Partial update from e3f3b445e2d20ac5d5b7fcb7559ce6beb55da0c9
in 4.9 branch.