[BUGFIX] Do not turn storages automatically offline

Storages should not be taken offline automatically.
Currently the storage turns offline if a configuration error is
detected.
But depending on the driver a configuration error can be a temporary
problem that just exists for seconds (like local filemount is
not available).

A storage should only be turned offline if you are in the backend
context
and the initialization fails.

Resolves: #75184
Releases: master, 7.6
Change-Id: Iddb18305f96df1a116a5d209bae41a73f5bb0ad2
Reviewed-on: https://review.typo3.org/49798


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Tested-by: Frans Saris <franssaris@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Sascha Egerer <sascha@sascha-egerer.de>