Add better coverage support under tox

For those in the community who don't use run_tests.sh but want
tox to have coverage support this small change should help.  It
adds coverage erase, combine, html reporting.  It also
fixes the coverage unit tests in two ways.  The first is
adding the locking like normal unit tests. The second
is adding substring regular expression matching to pick
a subset of tests.  This brings it up to closer par with
run_tests.sh.

Change-Id: If9ea229425dc9a191fa7c5cc073cf5da412a69b7
Support detection of fixed ip already in use

Update the validate_networks method to detect when a fixed ip is
already in use and raise the FixedIpAlreadyInUse exception

Change-Id: I07f83ce654c909b1158315dfc21a40654bc34a47
Closes-Bug: #1247844
Revert "Remove traces of now unused host capabilities from scheduler"

This reverts commit ce3f9e5fa9cd05f3ee3bb0cc7d06521d05901cf4.

This commit caused problems in tripleo, nova-bm isn't able to launch
instance as they are being filtered out by ComputeCapabilitiesFilter.

Fixes bug #1326289

Change-Id: Icaae95eea78eff11cee34e8a3875d62b3cce0b60
VMware: spawn refactor - phase 1 - test for spawn

Adding a test case for spawn to ensure all the correct methods are
called.  This test will get further fleshed out with explicit
assertions of behavior along with additional factoring pertaining to
image handling and manipulation.

partial blueprint vmware-spawn-refactor

Change-Id: Ia137f1ea4b9fa43741cdd7d610831da8e5474d62
Fix a wrong comment in the code

The docstring in the ExtensionManager class indicates a test file as
guide file, but the path reported is wrong.

Change-Id: I1b95d591cee6da3cc760c365c88ae1809973b98c
fix nova test_enforce_http_true unit test

When the nova policy patch was merged, causing
nova.tests.test_policy.PolicyTestCase.test_enforce_http_true to fail
randomly in the gate. The oslo has used the six.moves.urllib.request
instead of urllib2, but the patch didn't sync this in test_policy.

This related commit a88d9d5936aabc52046ed3ae566741422bfaed78.
Related-Bug: #1288178

Change-Id: I51b6bbf37b062edcf4c4b5f65adb8bfecd4a2eef
Merge "Revert "Remove traces of now unused host capabilities from scheduler""
Merge "VMware: spawn refactor - phase 1 - test for spawn"
Merge "fix nova test_enforce_http_true unit test"
Merge "Fix a wrong comment in the code"
Merge "Add better coverage support under tox"
Merge "Support detection of fixed ip already in use"