[BUGFIX] Scheduler: use img title-tags for mouse-over at status legend

[BUGFIX] Scheduler: use img title-tags for mouse-over at status legend

The 'Status Legend' in the Scheduler backend module does not use
<img title="" /> tags. Only <img alt=""> tags.
This patch writes the value from alt=""-Tag to title="" tag.

Thanks to Qitec for the original patch.

Change-Id: I401e3a129d8ef1dd7ea8c9d1130d1ed5ed1f6339
Resolves: #25661
Releases: 4.6
Reviewed-on: http://review.typo3.org/2446
Reviewed-by: Andy Grunwald
Tested-by: Andy Grunwald
Reviewed-by: Francois Suter
Tested-by: Francois Suter