Merge remote-tracking branch 'remotes/famz/tags/testing-pull-request' into staging

Testing patches

One fix for mingw build and some improvements in VM based testing, many thanks
to Paolo and Phil.

# gpg: Signature made Fri 26 Oct 2018 15:15:13 BST
# gpg:                using RSA key CA35624C6A9171C6
# gpg: Good signature from "Fam Zheng <famz@redhat.com>"
# Primary key fingerprint: 5003 7CB7 9706 0F76 F021  AD56 CA35 624C 6A91 71C6

* remotes/famz/tags/testing-pull-request:
  tests/vm: Do not abuse parallelism when HOST != TARGET architecture
  tests/vm: Do not use -enable-kvm if HOST != TARGET architecture
  tests/vm: Let kvm_available() work in cross environments
  tests/vm: Add a BaseVM::arch property
  tests/vm: Display remaining seconds to wait for a VM to start
  tests/vm: Do not use the -smp option with a single cpu
  tests/vm: Do not abuse parallelism when KVM is not available
  tests/vm: Extract the kvm_available() handy function
  tests: docker: update test-mingw for GTK+ 2.0 removal

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>