cmd/migratedb: ignore hash for .go migrations
cmd/migratedb: ignore hash for .go migrations

Sometimes go migrations need to be modified because of refactoring, renames, etc.

Closes chain/chainprv#822.
Reviewers: da39a3ee5e6b4b0d3255bfef95601890afd80709@tessr

chain/chain,chain/chain,chain/chain,chain/chain,chain/chain,chain/chain