It has no meaning to stay in election state when the primary master is
known. Also, it causes problems as the elected primary master will soon
start sending packets we don't expect while election is running.

handler/election.py:
- Receiving announcePrimary is enough to exit election immediately, so
  reach election end condition (both sets must be empty)
- Receiving answerPrimary with a known primary is enough to exit election
  immediately (don't attempt to connect to to primary master).
app.py:
- Apply PrimaryHandler while iterating over connections when the primary
  master connection is found, rather than once all other connections are
  closed.
- If no primary master connection was found, start establishing one.
handlers/secondary.py:
- Handle connectionCompleted event as we might only reach primary master
  once with this handler if connection was not established during election.
- Likewise, handle connectionFailed event, and treat it as a primary
  failure.
- Stop ignoring answerPrimary packets, instead check that advertised
  primary master is the expected one and request node identification.

git-svn-id: https://svn.erp5.org/repos/neo/trunk@1583 71dcc9de-d417-0410-9af5-da40c76e7ee4