Fix AvailabilityZone check for hosts in multiple aggregates

Check for multiple AZ was distinct when adding an host to an aggregate
and when updating an aggregate (or its metadata), which was leading to
possible corner-cases where logics were different.

This patch proposes a single way for checking for both API methods and
also adds an extra control on the possibility to have an aggregate with
its metadata AZ set to the configuration default value (eg. 'nova') and
where it was possible to subsequently have one host in two disctinct AZs
Fixed that scenerio as it is a gap, Nova as of now preventing to have
one host in two distinct AZs.

Change-Id: Ida6aa507f34f36a436adaafe1f7609963c59a9bc
Partial-Bug: #1277230
Make hacking test more accurate

Hacking check returns tuple or None, assertTrue/assertFalse doesn't
handle the return results properly. For example, non-tuple return value
also can pass the hacking unit test method.

  * use assertEqual or assertIsInstance instead of assertTrue
  * use assertIsNone instead of assertFalse
  * remove duplicated test data in method test_virt_driver_imports

Change-Id: Iee8b466c3ab2c6437144367cdb874bd2f8839984
Default dhcp lease time of 120s is too short

As part of reasonable-defaults, increase the default DHCP
lease time to a more sane value of 24 hours.  This change
also aligns Nova with the current default DHCP lease time
in Neutron.

DocImpact: This changes the default dhcp_lease_time from
120 seconds to 86400 seconds (24 hours).  If the Icehouse
or previous release behavior is desired, set the config
dhcp_lease_time to 120.

Change-Id: Ia666ff31f299c57d46605705e9ebea21630e0722
Closes-Bug: #1317654
Imported Translations from Transifex

Change-Id: Ifd9f15ab09275d15f42025e4698b4d4193e1157b
Merge "Make hacking test more accurate"
Merge "Default dhcp lease time of 120s is too short"
Merge "Imported Translations from Transifex"
Merge "Fix AvailabilityZone check for hosts in multiple aggregates"