tests/functional: return output from cmd.py helpers

Tests might want to look at the whole output from a command execution,
as well as just logging it. Add support for this.

Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250903201931.168317-2-john.levon@nutanix.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
1 file changed