Move StartupCLOG() calls to just after we initialize ShmemVariableCache.

Move StartupCLOG() calls to just after we initialize ShmemVariableCache.

Previously, the hot_standby=off code path did this at end of recovery,
while the hot_standby=on code path did it at the beginning of recovery.
It's better to do this in only one place because (a) it's simpler,
(b) StartupCLOG() is trivial so trying to postpone the work isn't
useful, and (c) this will make it possible to simplify some other
logic.

Patch by me, reviewed by Heikki Linnakangas.

Discussion: http://postgr.es/m/CA+TgmoZYig9+AQodhF5sRXuKkJ=RgFDugLr3XX_dz_F-p=TwTg@mail.gmail.com