testsutilsqemu: check return value of virQEMUCapsNewCopy

While for virQEMUCapsNew this should not be needed
(the possible failures in VIR_CLASS_NEW are only hit
 on bad API usage which we don't do here),
virQEMUCapsNewCopy calls into many other functions,
some of which actually fail.

Check the return value of both.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

tests/testutilsqemu.c

@@ -349,6 +349,9 @@ int qemuTestCapsCacheInsert(virFileCachePtr cache,
             tmpCaps = virQEMUCapsNew();
         }
 
+        if (!tmpCaps)
+            return -1;
+
         if (!virQEMUCapsHasMachines(tmpCaps)) {
             const char *defaultRAMid = NULL;