Run ulimit4.sh using /bin/bash to avoid noexec

Run ulimit4.sh using /bin/bash to avoid noexec

Panora200 on IRC reported the error "/bin/bash: bad interpreter:
Permission denied", which we tracked down to the fact that /var/www (or
whatever) was mounted noexec.  Prepending '/bin/bash ' to the command
line should fix it.  Not heavily tested -- I only checked that
wfShellExec() seemed to work from eval.php for trivial uses.