Currently, 'icmp', 'ipv6-icmp' and 'icmpv6' can be
specified as an IPv6 ICMP protocol value. This can
lead to duplicate entries in the DB for doing exactly
the same thing.
Change to always be 'ipv6-icmp' so this doesn't happen.
Existing rules using one of the old values will now be
returned with 'ipv6-icmp' as the protocol value.
Depends-on: https://review.opendev.org/660206
Depends-on: https://review.opendev.org/660387
Change-Id: I7cd146691dce1a690e1d2c309dfd54b4a0032f76
Partial-Bug: #1582500