Make log_file and notifier_strategy configurable

This makes log_file and notifier_strategy configurable in
/etc/glance/glance-api.conf and /etc/glance/glance-registry.conf.

There is corresponding change to tripleo-heat-templates to expose these
configurations in the heat templates at:
https://review.openstack.org/#/c/76652/

Change-Id: I0591f861fe292df4373839fc675481d2fa4fa5fc