[BUGFIX] Avoid race conditions between opening and closing modals

Cleaned up the TYPO3 Modal events so they do no conflict each other
and are bound the correct DOM elemens.

Further rely on the bs.modal events to set currentModal.

Resolves: #69977
Releases: master
Change-Id: I295a43c5d81c69c0338981ff0fa4a0c042b496ed
Reviewed-on: http://review.typo3.org/43438


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>