Configurable cookie name feature relies on a started PHP session in the
frontend. This is not desired. Thus, start time tracking a bit later.

Change-Id: Ia1bc200e1610b0b789b45e6d5525ae9011c0117a
Resolves: #30269
Releases: 4.6
Reviewed-on: http://review.typo3.org/6203
Reviewed-by: Susanne Moog
Tested-by: Susanne Moog
Reviewed-by: Wouter Wolters
Reviewed-by: Steffen Ritter
Tested-by: Steffen Ritter