manila service list shows up for uninitialized driver

[haixin]

there is a problem with a manila driver not initializing correctly, but the manila service is up.
For example, i add a new driver to manila.conf and enabled it, then i restart manila-share, i found
manila service-list shows the status of this driver is UP. but now this backend has not initialized yet,
that means this backend can not be "up" status before the driver initialized successed.

this bug will lead to some share action error, will return driver is uninitialized. although manila service-list shows "UP". so we need to fix it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/697957

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/697957
Committed: https://git.openstack.org/cgit/openstack/manila/commit/?id=37a9e5388d504b0e4e4c58c9f22d0703391378a0
Submitter: Zuul
Branch: master

commit 37a9e5388d504b0e4e4c58c9f22d0703391378a0
Author: haixin <email address hidden>
Date: Mon Dec 9 03:48:48 2019 -0500

    Don't send heartbeats if driver not initializing correctly

    This commit adds is_service_ready method to base Manager class that can be
    used to indicate that service is not ready or initialzed success. This is
    used to block refreshing Service heartbeats if manager will return false
    from is_service_ready.

    Closes-Bug:#1853940

    Change-Id: Ib85468c703dfa51b03d1838bd422c9b2669bc747