[BUGFIX] RTE: IE 11 always drops images at the end of text

IE needs a delay before the dialogue window gets closed.

Releases: master
Resolves: #64839
Change-Id: I02d49cb124370c23ba14f8617dd4019586e184ea
Reviewed-on: http://review.typo3.org/36642


Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>