qemuxml2xmltest: Remove pointless inactive->active testing

qemuxml2xmltest: Remove pointless inactive->active testing

'virDomainDefFormatInternalSetRootName' which is the top level XML
formatter function has the following condition as the very first thing:

     if (def->id == -1)
         flags |= VIR_DOMAIN_DEF_FORMAT_INACTIVE;

This makes it pointless to separately do inactive->active and
inactive->inactive XML -> XML testing as both will be in the end treated
as inactive->inactive.

This patch adds a warning to virDomainDefFormatInternalSetRootName and
removes the second pointless invocation of the test from
qemuxml2xmtest.

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