modernise radosgw systemd usage

[James Page]

Currently all ceph-radosgw unit use a common cephx key (radosgw.gateway).

Ideally each unit would have its own postfixed key (radosgw.`hostname`) which would allow switching the charms to use the newer ceph-radosgw@`hostname` systemd units rather than the older style init.d compat script radosgw.

This will require changes to the ceph-radosgw <-> ceph-mon relation to support generation of keys for the radosgw with a specific hostname attached.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/629147
Committed: https://git.openstack.org/cgit/openstack/charm-ceph-mon/commit/?id=d05704b05ffbfc32e6f4badc13aa5efa775019a8
Submitter: Zuul
Branch: master

commit d05704b05ffbfc32e6f4badc13aa5efa775019a8
Author: James Page <email address hidden>
Date: Tue Jan 8 10:02:04 2019 +0000

    Add support for RADOS gateway per unit cephx keys

    If ceph-radosgw units present a key_name attribute, then generate
    a cephx key using the key name and present back with the key_name
    as the prefix for the key.

    This switches radosgw units to having per-unit keys, rather than
    sharing a global key (required as part of the pre-work to support
    RADOS gateway federation).

    Change-Id: I289b75a2935184817b424c5eceead16235c3f53b
    Depends-On: I7ac4d23a91fa654b62afb62c389a8f9823ef2e05
    Closes-Bug: 1808140

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/629119
Committed: https://git.openstack.org/cgit/openstack/charm-ceph-radosgw/commit/?id=2858f1b02d6e5216234ff16a3feba34dae337538
Submitter: Zuul
Branch: master

commit 2858f1b02d6e5216234ff16a3feba34dae337538
Author: James Page <email address hidden>
Date: Mon Jan 7 17:18:07 2019 +0000

    Switch to using systemd units for radosgw

    Switch to using systemd configurations to manage radosgw instances;
    the radosgw init script is obsolete and will be removed at some
    point in time, and the newer style of managing radosgw daemons is
    inline with current best-practice.

    This changeset also changes the way cephx keys are issues; before
    all rgw instances shared a key, now a key is issued per host.

    The key is named 'rgw.`hostname`' to identify the application
    and host using the key.

    Existing deployments using the radosgw init script will be switched
    to use the new systemd named units; this occurs once the new key
    for the unit has been presented by the ceph-mon cluster over the
    mon relation. A small period of outage will occur as the radosgw
    init based daemon is stopped and disabled prior to the start of
    the new systemd based radosgw unit.

    This commit also includes a resync for charmhelpers to pickup
    support for '@' in NRPE service check names.

    Change-Id: Ic0d634e619185931633712cb3e3685051a28749d
    Depends-On: I289b75a2935184817b424c5eceead16235c3f53b
    Closes-Bug: 1808140