* master:
  Enable coverage for neo.tests, which is useful to find dead code
  Remove unused imports, found by pylint
  TODO: tweak should be safer
  Various neoctl/neolog formatting improvements/fixes
  debug: extend 'pdb' example to optionally break on an arbitrary list of callables
  client: fix simultaneous (re)connections to the master

- format IPv6 inside [] when followed by :<port>
- unify rendering of node lists
- neoctl: do not crash on empty DB (no PT id)

This fixes a reqression in commit c39d5c67,
which could leads to failures like:

2016-11-29 09:56:58,756 ERROR ZODB.Connection Couldn't load state for 0x4843
Traceback (most recent call last):
  File "ZODB/Connection.py", line 860, in setstate
    self._setstate(obj)
  File "ZODB/Connection.py", line 901, in _setstate
    p, serial = self._storage.load(obj._p_oid, '')
  File "neo/client/Storage.py", line 82, in load
    return self.app.load(oid)[:2]
  File "neo/client/app.py", line 352, in load
    data, tid, next_tid, _ = self._loadFromStorage(oid, tid, before_tid)
  File "neo/client/app.py", line 372, in _loadFromStorage
    for node, conn in self.cp.iterateForObject(oid, readable=True):
  File "neo/client/pool.py", line 91, in iterateForObject
    pt = self.app.pt
  File "neo/client/app.py", line 146, in __getattr__
    return self.__getattribute__(attr)
AttributeError: 'Application' object has no attribute 'pt'

* master:
  storage: fix crash when a client loses connection to the master just before voting
  no change: only some code reindentation
  Enable branch coverage measurement by default
  coverage: add support for functional tests

This is similar to commit 7aecdada
and for completeness, we also protect unlock the same way.

For 2 previous commits, we didn't reindent in order to keep the diff readable.

See 9385706f (Fix identification issues, including a race condition
causing id conflicts).

The added test describes how the new id timestamps fix the race condition.
These timestamps could be any unique opaque values, and the protocol is
extended to exchange them along with node ids.

Internally, nodes also reuse timestamps as a marker to identify the first
NotifyNodeInformation packets from the master: since this packet is a complete
list of nodes in the cluster, any other node in the node manager has left the
cluster definitely and is removed.

The secondary masters didn't receive update about master nodes.
It's also useless to send them information about non-master nodes.

When Client (including backup master) and admin nodes are identified,
the primary master now sends them automatically all nodes with
NotifyNodeInformation, as with storage nodes.

- check address conflicts
- on invalid values, reject peer instead of dying

Listing connected/connecting nodes with a UUID is used:
- in one place by storage nodes: here, it does not matter if we skip nodes that
  aren't really identified
- in many places by the master, only for server connections, in which case we
  have equivalence with real identification

So in practice, NodeManager is only simplified to reuse the 'identified'
property of nodes.