Fix saving ostree remote configs with gpg set.

Unmap 'gpg-verify' back to "true/false" when saving
ostree repo remote config. Config file is "true/false"
and mapped to bool on read. Creating a remote config
from a Content was passing that bool to config.set.
So Content blobs that actually populate gpgUrl were
failing writing remotes.
Merge pull request #976 from candlepin/alikins/ostree_config_bool

Fix saving ostree remote configs with gpg set.