Allow guest path to be omitted from NFS share

[staticshock]

I saw it mentioned in #936 that omitting the guest path prevents the auto-mount. I would like that behavior to be available to NFS shares. My use-case is Windows guests, where a normal NFS mount fails with this error:

Vagrant attempted to execute the capability 'mount_nfs_folder' on the detect guest OS 'windows', but the guest doesn't support that capability.

I have a work-around for mounting the drive myself, if vagrant just gave up the auto-mount attempt. Omitting the guest path, however results in this error:

vm:

• The shared folder guest path must be absolute: {:type=>"nfs"}

So, my VM initialization process is pretty bad: (1) comment out the NFS synced_folders from Vagrantfile, (2) vagrant up in order to get non-NFS folders mounted and to provision (3) uncomment NFS synced_folders (4) vagrant reload to create the NFS shares, after which vagrant fails due to the capability error.

[mitchellh]

You can explicitly set auto_mount: false. Err try mount_auto: false as well. I can't remember off the top of my head. We decided to go this route instead of the implcit not mounting.

[staticshock]

Thanks, good to know.