inconsistent time zone formats in log

The xlog code uses two different time zone formats at various times.
Here is an example:

2012-12-29 07:04:07.338 EST LOG:  database system was interrupted; last known up at 2012-12-29 06:27:02 EST
2012-12-29 07:04:26.347 EST LOG:  last completed transaction was at log time 2012-12-29 06:34:24.394802-05

The second format also does not respect log_timezone, which seems a bit
of a bug.

It's also not clear why we need three different ways to show
milliseconds within the space of two lines.

Could we make some of this more consistent?