Skip autoscaling test until more reliable

AutoScalingTest has issues which will require rethinking how
this test is implemented, including:
- the optimal ConsumeStopSeconds will depend on the overhead
  of boot time, which varies greatly between bare metal and
  virt-on-virt
- every combination of distro/release/flavor will result in a
  different baseline memory usage, making it difficult to
  determine the ScaleDownThreshold to set

This change skips this test and tracks against the bug:
Partial-Bug: #1257575

Change-Id: I0695a7efacdbeab39c895a97cb45496fcaf97e35
Separate negative tests in flavors/test_flavors

Separate negative tests to their own file. Restructured
invalid_id and nonexistent_id tests.

bp negative-test-files

Change-Id: I4b00353bcfef03e59cd3e628fb12774e0bbdcbd5
Fix Neutron VPNaaS Test

VPNService requires Router is connected to external gateway.
In this commit, we connected the test router to external network.

Change-Id: Ib87583219efd8efd959c9c7edb813c3a70e7d20c
Closes-Bug:1259282
Don't have tox install pre-release software

Override the tox pip install command to avoid using the "--pre" option
which is the default in tox.  "--pre" means "Include pre-release and
development versions."  By default, pip will only install stable
versions of software, and that is the behavior we want.

Change-Id: I3aa2a69c5bae54932137c78cc711236a0ca24602
Merge "Skip autoscaling test until more reliable"
Merge "Don't have tox install pre-release software"
Merge "Fix Neutron VPNaaS Test"
Merge "Separate negative tests in flavors/test_flavors"