tests/qtest/usb-hcd-uhci-test: Check whether "usb-storage" is available

The "usb-storage" device might not have been compiled into the binary
(e.g. when compiling with "--without-default-devices"), so we have to
check first before using it.

Message-Id: <20230525081016.1870364-2-thuth@redhat.com>
Reviewed-by: Ani Sinha <anisinha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
1 file changed