qtest: bump qom-test timeout to 15 minutes

qtest: bump qom-test timeout to 15 minutes

The qom-test is periodically hitting the 5 minute timeout when running
on the aarch64 emulator under GitLab CI. With an --enable-debug build
it can take over 10 minutes for arm/aarch64 targets. Setting timeout
to 15 minutes gives enough headroom to hopefully make it reliable.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20230717182859.707658-4-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20231215070357.10888-4-thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>