Client nodes ignored the state of the connection to the master node when reading
data from storage, as long as their partition tables were recent enough. This
way, they were able to finish read-only transactions even if they could't reach
the master, which could be useful for high availability. The downside is that
the master node ignored that their node ids were still used, which causes "uuid"
conflicts when reallocating them.

Rejected solutions:
- An unused NEO Storage should not insist in staying connected to master node.
- Reverting to big random node identifiers is a lot of work and it would make
  debugging annoying (see commit 23fad3af).
- Always increasing node ids could have been a simple solution if we accepted
  that the cluster dies after that all 2^24 possible ids were allocated.

Given that reading from storage without being connected to the master can only
be useful to finish the current transaction (because we always ping the master
at the beginning of every transaction), keeping such feature is not worth the
effort.

This commit fixes id conflicts in a very simple way, by clearing the partition
table upon primary node failure, which forces reconnection to the master before
querying any storage node. In such case, we raise a special exception that will
cause the transaction to be restarted, so that the user does not get errors for
temporary connection failures.