docs: Update docs to comply with Ganeti 2.10

The syntax of `gnt-network connect` command changed recently. This
commit updates networks.rst and the installation guides to comply with
the new syntax.
Merge pull request #318 from Erethon/hotfix-0.16.1

docs: Update docs to comply with Ganeti 2.10
webproject: Extend allocated xseg pool array

On gunicorn reload, extend allocated xseg pool per worker class
array until the already spawned workers exit. On a graceful worker
exit the previously allocated xseg pool is properly shutdown and
the new workers takeover the next series of xseg ports.
On a next reload basis the new workers will always take over the
previously allocated xseg pool ports. With this mechanism we always
need at least twice the number of workers in xseg ports per pool.

Care must be taken in xseg ports accounting and bookkeeping when
we dynamically change the number of workers by using the TTIN and
TTOUT signals sent to the master.

The total number of xseg ports allocated by all workers must not
exceed the minimum port being used by the Archipelago peers.
If the total amount of used ports exceeds this limit one should
rearrange the Archipelago peers ports along with the relevant
dynamic port range.
docs: Mention admin-app pooling incompatibility

snf-admin-app opens connections to multiple DBs, which means it cannot
use psycopg connection pooling. Advise the users to delete any
pooling-related options from 10-snf-webproject-database.conf (if, for
example, they copied it from the Astakos or the Cyclades node).
psycopg: Don't include conn info in exception

When trying to get a pooled_psycopg2 connection, the _get_pool() method
checks the connection args against the pool args and raises an exception
if the two differ. This leads to an internal server error, which results
in logging the connection and pool info / args, which include the DB
password, and, depending on the deployment, it might also send them via
email to the admins. Log the connection and pool args only when log
level is set to  debug, and remove them from the exception message, so
that they won't end up being send via email.