SERVER-13627 Test that replSetReconfig prohibits 0-vote arbiter.

This re-applies commit 6eccc037b1e6d22d60d0e7aec39dcc183a756790 with a fix
for occasional failures of zero_vote_arbiter.js:

    Don't assume that the first member started is always the primary.

Closes #856

Signed-off-by: Benety Goh <benety@mongodb.com>