Associate MAINLINE_NETWORK_STACK with net_raw and net_admin gid

Provide network stack the permission to access eBPF maps for tethering
offload

Test: m
Test: cat /proc/<pid>/status of network_stack has net_raw (3004) and
      net_admin (3005)

$ adb shell cat /proc/<pid>/status | egrep "Name|Uid|Gid|Groups"
Name:   rkstack.process
Uid:    1073    1073    1073    1073
Gid:    1073    1073    1073    1073
Groups:	1073 3001 3002 3003 3004 3005 3006 3007 9997

Change-Id: Ib3f6094e4c846832e44497466e3fed7dcd125593