[SECURITY] XSS in Scheduler Example Task

The scheduler test-task that sends an email does not properly
sanitize the input of the email field when rendering the editing
form of that task.

Change-Id: Ic77e50b339488acb5b811e35aaa558e26ac6193e
Fixes: #30967
Releases: 6.0, 4.7, 4.6, 4.5
Security-Commit: d72a6e273edb2e249c1f544f0d6b7139aecdc825
Security-Bulletin: TYPO3-CORE-SA-2012-004
Reviewed-on: http://review.typo3.org/13770
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader