common: LogClient: allow specifying facility for LogClient

Instead of allowing only one LogClient, we will now allow any daemon to
have any number of LogClients.  They may either all log to the default
facility and level, or they may see their facility and level specified
upon creation (via a new constructor).

This patch also changes 'handle_log_ack' in such a way that the LogClient
will handle all acks with bearing the LogClient's facility, or will
otherwise simply ignore them.  The function will return true whenever the
message has been handled or false if that was not the case.  It will fall
on the caller the responsibility of deciding whether the message will be
passed to other LogClients or not, and when it is to be release.

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
common: LogEntry: if 'channel' is empty on decode assign default

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: Monitor: log every administrative action in an 'audit log'

Fixes: #7988

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: Monitor: log administrative actions via admin socket

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: Monitor: propagate return for functions called for admin socket

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: Monitor: observe log client config changes

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: Monitor's clog/audit_clog need to accessed as pointers

:1,$s/clog\./clog->/

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
DNM: mon: LogMonitor: write log messages on a per-channel basis

Instead of dumping everything to the same log file, let us this way
allow a user to specify per-channel log files.

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: LogMonitor: observe config changes

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: LogMonitor: (un)register conf observer at init/shutdown

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: LogMonitor: expand meta variables at time-of-call

Instead of expanding it when we updated config options, as that would be
nothing but trouble.

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
mon: LogMonitor: debug update_from_paxos

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
osd/mds/monc: Adjust for LogClient/LogChannel usage

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>