server: Avoid deadlock in daemon_log().

server: Avoid deadlock in daemon_log().

Currently both the generic signal handler in signal.c and the signal
handler for the stat command handler in command.c call daemon_log()
via PARA_EMERG_LOG(). This is problematic because daemon_log()
takes the log mutex and the signal might arrive while daemon_log()
is executing. If this race condition is hit, the process deadlocks
because daemon_log() tries to acquire a mutex which it already holds.

All three types of server processes (main, afs and command handler)
are susceptible to this bug, but regardless of which process happens
to hit the race window, the server process hangs waiting on the mutex,
and no longer accepts connections.

Fix this by removing the problematic log call in the generic case and
by printing it out of interrupt context in the command handler case.

This bug was introduced together with the log mutex five years ago.

Fixes: ced0c17d1a3ee0336dc7b35e69faff131dabecac