pvattest: Fix successful 'check' evaluation

Invert the polarization of the successful state. The checks are
considered to be successful if there are no issues. Therefore, test for
an empty issue list and not for a non-empty.

Fixes: 697dcc0f6b ("rust/pvattest: Add check command")
Reported-by: Reinhard Buendgen <buendgen@de.ibm.com>
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/pvattest/src/cmd/check.rs

@@ -129,7 +129,7 @@ pub fn check(opt: &CheckOpt) -> Result<ExitCode> {
     firmware_check.check(&mut issues);
 
     let res = CheckResult {
-        successful: !issues.is_empty(),
+        successful: issues.is_empty(),
         issues,
         image_host_key,
         attest_host_key,