In I9a934bda3 base64 decoding was changed from using commons-codec
library to Guava library. However, this broke users who specify not only
base 64 encoded key, but also provide comment, similar to authorized
keys format without leading algorithm.
Clarify the documentation what format is supported in peer keys file and
skip the comment part if provided.
Also add integration test for peer keys authentication with three use
cases:
1. Test format: <key_material comment>
2. Test format: <key_material>
3. No peer keys file present
Test Plan:
$ bazel test javatests/com/google/gerrit/integration/ssh:peer-keys-auth
Bug: Issue 12884
Change-Id: Id748cb55497e3347477012911f716ac5b7b69863
90bed3f243