This helper will simplify a bunch of code checking for QMP errors and
can be shared by various tests.  Note that test-qga does check for
error description as well, so don't replace the code there for now.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>