[BUGFIX] Set correct cookie when permalogin is enabled

Although permalogin is enabled we set a session cookie.
This happens because setSessionCookie is called too early
and we do not know yet whether the session should be permanent
and an according cookie shall be set or not.

Solution is to set $this->dontSetCookie = FALSE
which triggers setting the cookie at an appropriate time.

Resolves: #60264
Releases: 6.3, 6.2
Change-Id: Iad5ce8597f90c4a607a43ea4d3368d117fa6b4ed
Reviewed-on: http://review.typo3.org/31754
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>