Support empty folder in SearchFlag.VirtualMachines
Support empty folder in SearchFlag.VirtualMachines

When using vm.info on an empty folder, ErrNotFound would be
returned and additional arguments would be skipped without error.
For example, the following would exit 0 with no output:
 govc vm.info empty-folder/* non-empty-folder/*

jrmycanady/govmomi,dougm/govmomi,RotatingFans/govmomi,higebu/govmomi,casualjim/govmomi,excilsploft/govmomi,egorovv/govmomi,higebu/govmomi,ilikejam/govmomi,casualjim/govmomi,jrmycanady/govmomi,excilsploft/govmomi,mevansam/vsphere-govmomi,mevansam/vsphere-govmomi,austinlparker/govmomi,casualjim/govmomi,ilikejam/govmomi,cgtexmex/govmomi,dougm/govmomi,vmware/govmomi,bruceadowns/govmomi,austinlparker/govmomi,excilsploft/govmomi,vmware/govmomi,cgtexmex/govmomi,egorovv/govmomi,vmware/govmomi,RotatingFans/govmomi,austinlparker/govmomi,caglar10ur/govmomi,bruceadowns/govmomi,RotatingFans/govmomi,caglar10ur/govmomi,bruceadowns/govmomi,jrmycanady/govmomi,cgtexmex/govmomi,mevansam/vsphere-govmomi,frapposelli/govmomi,ilikejam/govmomi,frapposelli/govmomi,egorovv/govmomi,dougm/govmomi,higebu/govmomi,caglar10ur/govmomi,frapposelli/govmomi