Changed default scan_via_host value to false.

This value was originally set to true to ensure vddk scanning did not send all disk data through the VC.  This is not a realistic concern as VC returns a handle the the host for communication.

Switching the default value also removes the need to add host credentials solely for the purpose of VM scanning on VMware.
@brandondunne Good question.  @roliveri Is there any advantage to leaving this exposed as a configuration value?  Would anyone need to control if the VM scan connection is initiated through the host instead of VC?

If this does not need to be exposed then there is other code that could also be removed as well.