vmx: Relax virtualHW.version check

vmx: Relax virtualHW.version check

The original implementation of the VMX config parser assumed that the
virtualHW.version would have more influence on the content of the VMX
file than it actually seems to have. It started with accepting only
version 4. Additonal versions were added later without any additional
changes in the parser itself. This suggests that the influence of the
virtualHW.version on the content and format of the VMX file is small
or non-existent.

The parser worked without any changes across several virtualHW and
vSphere versions. So instead of adding new virtualHW.version values to
the parser as they come along, or adding an extra flag to allow unknown
virtualHW.version values just relax the check to require version 4 or
later.