Set /proc/sys/kernel/dmesg_restrict to 1

Set dmesg_restrict to 1 to help limit inadvertent information leaks
from the kernel to non-privileged programs.  Root and programs with
CAP_SYSLOG will continue to have access to dmesg output.

See "dmesg_restrict" in Documentation/sysctl/kernel.txt from the
Linux kernel source code.

Bug: 5585365
Change-Id: Iffcf060ea4bd446ab9acf62b8b61d315d4ec4633