Fix coverity complain in commandtest.c

For a "newfd1" the coverity tools thinks that the fd is closed in
a "virCommandPassFD", but with "flags == 0" it cannot be closed.

The code itself is ok, but coverity tool thinks that there is
"double_close" of the "newfd1" and to prevent showing this error
we simply add a comment before the proper close.

This has been found by coverity.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>

tests/commandtest.c

@@ -215,6 +215,7 @@ static int test3(const void *unused ATTRIBUTE_UNUSED)
 
 cleanup:
     virCommandFree(cmd);
+    /* coverity[double_close] */
     VIR_FORCE_CLOSE(newfd1);
     VIR_FORCE_CLOSE(newfd2);
     return ret;