fix whitespace
ssh_authorized_keys: shell-escape the login

When the login is put into the env var for the command run as the shell,
it needs to be escaped so it doesn't become a command itself.

Bug 1134139 - [RFE] Track real person for gear SSH logins
https://bugzilla.redhat.com/show_bug.cgi?id=1134139
ssh keys: remove special logins

Users with single-char logins should still be logged, and there doesn't
seem to be a good purpose for the special 'S' and 'A' logins. So, they
are now removed.

Bug 1134139 - [RFE] Track real person for gear SSH logins
https://bugzilla.redhat.com/show_bug.cgi?id=1134139