Mark netd as updatable in its rc file.

netd itself is not updatable, but on startup it dlopen()s the
resolver library from the DNS resolver APEX. Mark it as updatable
so init won't start it until all APEX packages are ready.

Bug: 121354779
Test: netd doesn't crash on startup
Change-Id: I7d0d0ec39295a070065cef60944ee54e06ab0297