Logging: Map TEVENT_DEBUG_FATAL to DEBUG_CRIT

Logging: Map TEVENT_DEBUG_FATAL to DEBUG_CRIT

This is currently mapped to DEBUG_EMERG.  CTDB really has no business
logging anything at EMERG level since the whole system is not about to
abort or catch fire.  EMERG causes the message to appear on the
console and on every terminal.  That's a bit overzealous!

There would be very few situations where logs are being filtered at
level below ERROR, so CRIT should certainly suffice.

The trigger for this was curious messages saying "No event for <n>
seconds!" logged in a user's terminal.

Pair-programmed-with: Amitay Isaacs <amitay@gmail.com>
Signed-off-by: Martin Schwenke <martin@meltin.net>