qtest: add migration testing

Hi,

Add a basic qtest for migration testing. Currently, it just tests a migrate of machine 'pc' on the same host. Would be nice to extend to multiple machine versions, but that requires multiple binaries, which could be done, but is perhaps a bit awkward from qtest? Testing different machine versions within the same binary doesn't seem like a real world test case to me. Currently, the test aborts, if the migrate takes more than 2 minutes.

In any case, the test currently fails for q35, since ahci migration suport isn't in place. Thus, I intend to add q35 testing here, once those ahci migration patches are accepted.

Thanks,

-Jason

v2:
* move core migration functions to libqtest.c
* simplify Makefile dependencies
* use 'mkdtemp()' instead of child pid to identify qemu instances

Jason Baron (3):
qtest: Enable creation of multiple qemu instances
qtest: extend qtest_qmp() to fill in the reply
qtest: add migrate-test

 tests/Makefile       |    4 +-
 tests/libqtest.c     |  130 ++++++++++++++++++++++++++++++++++++++++++++------
 tests/libqtest.h     |   30 ++++++++++--
 tests/migrate-test.c |   68 ++++++++++++++++++++++++++
 4 files changed, 212 insertions(+), 20 deletions(-)
 create mode 100644 tests/migrate-test.c