salt-ssh: Do not attempt to match host/ip to minion ID if reverse lookup fails
salt-ssh: Do not attempt to match host/ip to minion ID if reverse lookup fails

When the reverse lookup fails, `salt.utils.network.ip_to_host()` returns
`None`. Later, when we attempt to look through the roster(s) for a minion ID
matching the target's host, a roster entry without a `host` key will
mean that `roster_data.get('host')` evaluates as None. This causes the
target expression to be expanded as `None`, when what we should do is
simply carry on without attempting to find a match in the roster(s).
This commit does just that.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt