More recent versions of Gerrit (somewhere between the 2.8 we were
running and the 2.11 to which we upgraded) switched some common
groups to be virtual routines, for example the Registered Users
group, so they no longer appear in the groups list. However we
should also not be counting members of these virtual groups as
approvers anyway (even though in the case of the sandbox repo they
are), so filter them out of the assembly loop in who-approves.py to
prevent it from breaking when it encounters them in an ACL.
Change-Id: Ibb73b68e6338cd2fe2e18c09993d6e02b03c312a
31eab4a00d