Merge remote-tracking branch 'remotes/huth-gitlab/tags/pull-request-2019-09-05-v2' into staging

- Make the core libqtest library independent from global_qtest
- Clean up docs from hard-coded qemu-system-* names
- Install libattr-dev and libcap-dev in gitlab-ci to test virtio-9p

# gpg: Signature made Thu 05 Sep 2019 15:52:30 BST
# gpg:                using RSA key 27B88847EEE0250118F3EAB92ED9D774FE702DB5
# gpg:                issuer "thuth@redhat.com"
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full]
# gpg:                 aka "Thomas Huth <thuth@redhat.com>" [full]
# gpg:                 aka "Thomas Huth <huth@tuxfamily.org>" [full]
# gpg:                 aka "Thomas Huth <th.huth@posteo.de>" [unknown]
# Primary key fingerprint: 27B8 8847 EEE0 2501 18F3  EAB9 2ED9 D774 FE70 2DB5

* remotes/huth-gitlab/tags/pull-request-2019-09-05-v2:
  gitlab-ci.yml: Install libattr-devel and libcap-devel to test virtio-9p
  qemu-doc: Do not hard-code the name of the QEMU binary
  tests/vm: Take the J=x setting into account for the vm-boot-ssh targets, too
  tests/libqtest: Use libqtest-single.h in tests that require global_qtest
  tests/libqtest: Move global_test wrapper function into a separate header
  tests: Remove unnecessary global_qtest references
  tests/libqos: Replace clock_step with qtest_clock_step in virtio code
  tests/libqos/e1000e: Make e1000e libqos functions independent from global_qtest
  tests/migration: Do not use functions anymore that rely on global_qtest

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