Bug 18821: (QA follow-up) Last tweaks for performance

Bug 18821: (QA follow-up) Last tweaks for performance

[1] passing unsafe has no use since it is a scalar, removed it to unconfuse
[2] remove caching when pref is disabled
[3] caching userid removes the need for calling Patron->find each time
[4] subsequent changes in unit test
[5] cosmetic renames to move from session to daily basis (changed dev angle)

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
First call going thru Koha::Patron takes about 0.0150 sec.
Subsequent calls only use caching and take about 0.0006 sec.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>