puppet provisioner nfs support

A sample `vagrant provision` run on my system with this patch:

    $ mount | grep puppet
    192.168.33.1:/home/marc/vagrant/puppetmaster/manifests on /tmp/vagrant-puppet/manifests type nfs (rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.33.1,mountvers=3,mountport=32767,mountproto=udp,local_lock=none,addr=192.168.33.1)
    192.168.33.1:/home/marc/vagrant/puppetmaster/modules on /tmp/vagrant-puppet/modules-0 type nfs (rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.33.1,mountvers=3,mountport=32767,mountproto=udp,local_lock=none,addr=192.168.33.1)
    192.168.33.1:/home/marc/vagrant/puppetmaster/site-modules on /tmp/vagrant-puppet/modules-1 type nfs (rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.33.1,mountvers=3,mountport=32767,mountproto=udp,local_lock=none,addr=192.168.33.1)
    [...]
    notice: Finished catalog run in 49.05 seconds
    Changes:
                Total: 1
    Events:
                Total: 1
              Success: 1
    Resources:
          Out of sync: 1
              Changed: 1
                Total: 421
              Skipped: 6
    Time:
               Sysctl: 0.00
            Mailalias: 0.00
               Sshkey: 0.00
            Resources: 0.00
           Filebucket: 0.00
                Group: 0.00
              Vcsrepo: 0.01
                 Host: 0.01
               Pgconf: 0.01
            File line: 0.01
              Sudoers: 0.02
                 User: 0.05
              Package: 0.53
             Last run: 1372095748
               Augeas: 2.50
                 File: 2.81
                 Exec: 25.08
              Service: 3.40
       Config retrieval: 45.95
                Total: 80.40
    [...]
    real    1m54.600s
    user    0m1.364s
    sys     0m0.336s


Using VirtualBox's default vboxsf filesystem:

    $ mount | grep puppet
    none on /tmp/vagrant-puppet/manifests type vboxsf (rw,nodev,relatime)
    none on /tmp/vagrant-puppet/modules-0 type vboxsf (rw,nodev,relatime)
    none on /tmp/vagrant-puppet/modules-1 type vboxsf (rw,nodev,relatime)
    [...]
    notice: Finished catalog run in 137.20 seconds
    Changes:
                Total: 1
    Events:
              Success: 1
                Total: 1
    Resources:
          Out of sync: 1
              Changed: 1
                Total: 421
              Skipped: 6
    Time:
               Sysctl: 0.00
              Vcsrepo: 0.00
           Filebucket: 0.00
               Sshkey: 0.00
            Mailalias: 0.00
            Resources: 0.00
                Group: 0.00
            File line: 0.02
                 Host: 0.02
               Pgconf: 0.02
              Sudoers: 0.03
                 User: 0.06
              Package: 0.65
             Last run: 1372096720
       Config retrieval: 169.33
                Total: 198.24
                 File: 2.11
               Augeas: 2.71
              Service: 2.89
                 Exec: 20.36
    [...]
    real    5m21.574s
    user    0m1.376s
    sys     0m0.380s