tests/avocado: Make ssh_command_output_contains() globally available This function will be useful in other tests, too, so move it to the core LinuxSSHMixIn class. Signed-off-by: Thomas Huth <thuth@redhat.com> Reviewed-by: Cédric Le Goater <clg@kaod.org> Message-Id: <20230421110345.1294131-2-thuth@redhat.com> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20230424092249.58552-9-alex.bennee@linaro.org>