qemuxml2xmltest: Parse all input files as inactive

qemuxml2xmltest: Parse all input files as inactive

In previous patches we've added testing of XML's explicitly parsed as
active (ensuring that it e.g. has a domain id) formatted into both
active and inactive versions.

Now qemuxml2xmltest can be simplified by making it test only XMLs parsed
as inactive.

To do this we pass VIR_DOMAIN_DEF_PARSE_INACTIVE in parseFlags. This
will also cause that all output files will become identical so the setup
of the test cases can be simplified by using the non-split output file
name.

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