Add release notes for 15.0.1 Ocata bug fix release

There are several high severity, high impact bug fixes going
into the upcoming 15.0.1 Ocata release. This change adds release
notes highlighting the most important fixes along with a known
issue for another regression bug that is not yet fixed in Ocata,
but should be shortly.

Change-Id: I06921fed0b1acdd48a23f24b5c42c19f9fb032e4

releasenotes/notes/ocata-15.0.1-fixes-d7f46a61a23d1566.yaml

@@ -0,0 +1,41 @@
+---
+prelude: >
+    The 15.0.1 Ocata release contains fixes for several high severity, high
+    impact bugs. If you have not yet upgraded to 15.0.0, it is recommended to
+    upgrade directly to 15.0.1.
+issues:
+  - |
+    There is a known regression in Ocata reported in `bug 1671648`_ where
+    server build failures on a compute node are not retried on another compute
+    node. The fix for this bug is being worked and will be provided shortly in
+    a 15.0.2 release.
+
+    .. _bug 1671648: https://launchpad.net/bugs/1671648
+critical:
+  - |
+    `Bug 1670627`_ is fixed. This bug led to potential over-quota errors after
+    several failed server build attempts, resulting in quota usage to reach the
+    limit even though the servers were deleted.
+
+    Unfortunately the ``nova-manage project quota_usage_refresh`` command will
+    not reset the usages to fix this problem once encountered.
+
+    If the project should not have any outstanding resource usage, then one
+    possible workaround is to delete the existing quota usage for the project::
+
+      ``nova quota-delete --tenant <tenant_id>``
+
+    That will cleanup the ``project_user_quotas``, ``quota_usages`` and
+    ``reservations`` tables for the given project in the ``nova`` database and
+    reset the quota limits for the project back to the defaults defined in
+    nova.conf.
+
+    .. _Bug 1670627: https://launchpad.net/bugs/1670627
+fixes:
+  - |
+    `Bug 1665263`_ is fixed. This was a regression where
+    ``instance.delete.start`` and ``instance.delete.end`` notifications were
+    not emitted when deleting an instance in ``ERROR`` state due to a failed
+    build.
+
+    .. _Bug 1665263: https://launchpad.net/bugs/1665263