tests/qtest: Bump qmp-cmd-test timeout to 120s

tests/qtest: Bump qmp-cmd-test timeout to 120s

The qmp-cmd-test test takes typically about 15s on my local machine.
On the k8s runners it takes usually 20s but sometimes about 60s,
because the k8s runners have wildly variable execution time.  If
they're running slow, we hit the default timeout.  Bump the
qmp-cmd-test timeout to 120s to avoid this.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-id: 20241008141337.2790423-1-peter.maydell@linaro.org