Revert "Make the xtables lock readable only by AID_RADIO and root."

This reverts commit 5e801e7b.

The file permissions don't allow access to the lock on devices
where vendor code runs with UID root and GID radio. They are
no longer necessary because we have a more flexible selinux-based
solution in https://android-review.googlesource.com/#/c/354223/ .

Test: strace -f -e flock -p <netmgrd_pid> on angler shows flock succeeds
Test: strace -f -e flock -p <netmgrd_pid> on marlin shows flock succeeds
Test: netd_unit_test passes on marlin
Test: strace -f -e flock -p <netd_pid> on marlin shows flock succeeds
Bug: 36108349
Bug: 37483189
Change-Id: Ia1bbf8d93ec6777514be66cbd1a32dfc95df95c0