In tests/qemuagenttest.c, the Timeout test should always be
called last. Any additional tests should come before this.
Signed-off-by: NEric Blake <eblake@redhat.com>

If VIR_TEST_EXPENSIVE is enabled, test timeout of agent commands. This
test takes 6 seconds to finish.

Exercise the arbitrary command passthrough API.

The shutdown test utilizes waiting for condition to exit the test. This
addition will return an error for the shutdown command to see if the
condition waiting code will not hang.

Coverity complained about unused variable that contains the shutdown
mode. The original intention was to check it against the requested mode.

Also the fixed check revealed a mistake in the expected shutdown mode.

Reported by John Ferlan.

This patch exports a few utility functions and adds testing of shutdown
commands of the guest agent.

Add a basic test framework with two simple tests to test guest agent
interaction.