Rollback quota when confirm resize concurrently completed

quota is reserved when confirm_resize is executed, if a concurrent
operation updated the status of migration, currently compute layer
will directly return back without rollback the quota and it can
lead to quota inconsistent issue layer.

Change-Id: I2217e9a4523d2783eccd8ef31c1fd65a604e2cc3
Closes-Bug: #1301690
Add _security_group_ensure_default() DBAPI method

According to the convention we use for DB API methods, every public
method should have a private counterpart. The difference between
those two is that the latter accepts an optional 'session' argument,
which makes it possible for the method to participate in the existing
database transaction.

security_group_ensure_default() was called inside instance_create()
and thus implicitly created a new concurrent db transaction, which
is now fixed by making a call to a private counterpart and passing
the session instance.

Closes-Bug: #1362233

Change-Id: Ifa1b6430328fde1ab0984f726bd8392bbd3f7ee5
the headroom infomation is incomplete

If multiple resources beyond the quotas in 'limit_check' from
nova/quota.py. The headroom information about the resources
beyond the quotas in OverQuota Exception is incomplete.

Change-Id: I790c22e3618a3558dfad64bf46e37e4e49f6385e
Closes-Bug: #1334965
Fix 'force' parameter for quota-update

Commit 77b4012a02c6b4827a7a6b112f35deb9ce94c395 added further
validation on the quota update controller that isn't aware of the
'force' parameter. This validation also duplicated the existing
validation that *did* honour 'force'.

This change merges the two validation methods and ensures that the
validation is skipped when the 'force' parameter is passed in the
request.

Change-Id: I25e3ce857a83cb50789a2a61bb01c796128ff4f8
Closes-bug: #1362405
Raise an exception if qemu-img fails

Raise an exception if the qemu image doesn't
exist or qemu-img fails.

Co-Authored-By: Chuck Short <chuck.short@canonical.com>
Closes-Bug: #1168318
Change-Id: I6b4123590e7d2934de0bc6add900d708d5986039
Merge "Raise an exception if qemu-img fails"
Merge "Fix 'force' parameter for quota-update"
Merge "the headroom infomation is incomplete"
Merge "Rollback quota when confirm resize concurrently completed"
Merge "Add _security_group_ensure_default() DBAPI method"