Fix mismatched tags (struct vs. class) inconsistency

Signed-off-by: Thorsten Behrens <tbehrens@suse.com>
Merge pull request #2067 from thorstenb/wip-janitorial-clang-3

[werror] Fix mismatched tags (struct vs. class) inconsistence

Reviewed-by: Sage Weil <sage@redhat.com>
mds: make MDS.replay_done clearer

... and add some assertions.

Signed-off-by: John Spray <john.spray@redhat.com>
mds: refactor MDS boot

* Make boot_start private.
* Define boot stages in enum, replace int with type.
* Merge steps 0 and 1, 0 always fell through to 1.
* Replace switch() with breaks with series of if()

Signed-off-by: John Spray <john.spray@redhat.com>
mds: introduce explicit DaemonState instead of int

Signed-off-by: John Spray <john.spray@redhat.com>
mds: handle replaying old format journals

To get back to the reformatting procedure that otherwise
occurs during MDLog::open, introduce an MDLog::reopen call
that MDS can use in the standbyreplay->standby transition
for the special case where the journal is old.

Fixes: #8869

Signed-off-by: John Spray <john.spray@redhat.com>