Slightly refactor signal handling and fd closing

Reformat (partially) to Android 4-space indentation style.

Test: as follows
    - built
    - flashed
    - booted
    - started and stopped tethering,
      observed normal dnsmasq behaviour
Bug: 38364896
Change-Id: I9b7775ee9ceccb8cf901d9262bc98f55e9cbbc11
1 file changed