metadata: group metadata next to description

metadata: group metadata next to description

It's better to group all the metadata together.  This is a
cosmetic output change; since the RNG allows interleave, it
doesn't matter where the user stuck it on input, and an XPath
query will find the same information when parsing the output.

* src/conf/domain_conf.c (virDomainDefFormatInternal): Output
metadata earlier.
* docs/formatdomain.html.in: Update documentation.
* tests/domainsnapshotxml2xmlout/metadata.xml: Update test.
* tests/qemuxml2xmloutdata/qemuxml2xmlout-metadata.xml: Likewise.