Update git submodules

* Update nova from branch 'master'
  to 681f6872fb3fbca290cfc3ff15d34b1d1ba6642d
  - Merge "testing: Use inspect.isfunction() to check signatures"
  - testing: Use inspect.isfunction() to check signatures
    
    We recently discovered that nova.test.SubclassSignatureTestCase has not
    worked properly since support for python 2.7 was dropped.
    
    The reason is the use of the inspect.ismethod() function; in python 2.7
    it returned true if the object was a bound or an unbound method [2] but
    as of python 3, it only returns true if the object is a bound method
    [2].
    
    Because of this, LibvirtBaseVolumeDriverSubclassSignatureTestCase was
    not actually checking any signatures.
    
    This replaces the use of inspect.ismethod() with inspect.isfunction()
    to fix the issue.
    
    It also adds a skip for subclass private functions as these are
    expected to be different among subclasses.
    
    One subclass method signature caught by the test is also updated to
    match the base class.
    
    [1] https://docs.python.org/2.7/library/inspect.html#inspect.ismethod
    [2] https://docs.python.org/3.5/library/inspect.html#inspect.ismethod
    
    Closes-Bug: #2019772
    
    Change-Id: I5644effac7206035de77e0d1cd450a9fb96c3a0d

nova

@@ -1 +1 @@
-Subproject commit da918d4b958d1f1c828e84d2a5c87c2dca676c39
+Subproject commit 681f6872fb3fbca290cfc3ff15d34b1d1ba6642d