Modernize style of kdb_log.c

ulog_get_entries had an unreachable branch which was removed during
de-indentation.
Fix iprop log reinitialization

If the master iprop log is reinitialized to serial number 0, slaves
will need to take a full dump--but after that happens, we need to know
whether the slave has taken that full dump, we we don't offering full
dumps indefinitely.

So, record a timestamp in kdb_last_time when we reinitialize the log
header, and compare the slave timestamp to kdb_last_time whenever it
has the current serial number, even if it's 0.  Test this by
performing a propagation with sno 0 in t_iprop.py and detecting
whether kpropd gets a second UPDATE_FULL_RESYNC_NEEDED response from
kadmind.

ticket: 7550 (new)