More specific Solaris <11 detection.

Note: This will probably break on Solaris 12+, but not certain of a better approach for now.

This is specifically an issue for the Solaris detection and operation due to the following conflicting lines:
Solaris 10: https://github.com/mitchellh/vagrant/blob/master/plugins/guests/solaris/config.rb#L14
Solaris 11: https://github.com/mitchellh/vagrant/blob/master/plugins/guests/solaris11/config.rb#L18

This has resolved the issues I had when building a Solaris base box with Packer and bringing up with Vagrant due to incorrect network device prefix.