Low: pacemakerd,libcrmcommon: don't touch kernel.sysrq

On Linux, Pacemaker previously enabled rebooting via SysRq by changing
/proc/sys/kernel/sysrq, then triggered the reboot via /proc/sysrq-trigger (as
root). However, per the kernel sysrq.txt documentation:

"Note that the value of /proc/sys/kernel/sysrq influences only the invocation
via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always
allowed (by a user with admin privileges)."