This improvement is part of a wave of polish
in preparation for the launch of the Ceph product.
In config.yaml, improve 'osd-journal' option description.
Also modernise example values for 'source' and use
consistent words with the ceph-osd, ceph-mon, and ceph-fs
charms.
This patch (in charms.ceph [1], copied here) add the concept of a
watchdog to the upgrade_monitor so that the charm can achieve two
objectives of 1. Waiting for much longer, but 2. detecting whether the
previous node has died / gone away. This is needed for 'large' OSDs
where the time to upgrade a node may exceed the current limit of 10
minutes, but also not to wait for 30 minutes on a dead previous node.
The watchdog implements two timeouts and an addition 'alive' key from
the previous node to indicate that it is still running. Otherwise,
functionality is identical.
[1] See depends on below
Depends-On: Ia450e936c2096f092af3be5a369b7abaf5023b16
Closes-Bug: #1762852
