[TASK] Ignore pcntl_* php function in disable_functions check

The check for disable_functions gives a warning on a Ubuntu OS.
To not give a false alarm we set the status to Notice if
only functions are disabled that are currently not used by TYPO3.

Change-Id: I2cc6de83dc805faf65f68e8c315b68a2f2576e81
Resolves: #46877
Releases: 6.1
Reviewed-on: https://review.typo3.org/19524
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn