vmx: Rework virVMXConfigScanResultsCollector slightly

vmx: Rework virVMXConfigScanResultsCollector slightly

The idea here is that virVMXConfigScanResultsCollector() sets the
networks_max_index to the highest ethernet index seen. Well, the
struct member is signed int, we parse just seen index into uint
and then typecast to compare the two. This is not necessary,
because the maximum number of NICs a vSphere domain can have is
(<drumrolll/>): ten [1]. This will fit into signed int easily
anywhere.

1: https://configmax.esp.vmware.com/guest?vmwareproduct=vSphere&release=vSphere%208.0&categories=1-0

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Tim Wiederhake <twiederh@redhat.com>