vagrant: switch to use out of tree build

vagrant: switch to use out of tree build

Vagrant shared folder, at least on the default virtual box, does not
support the creation of the socket files. If one were to build OVS
under /vagrant, 'make check' would not work.

Out of tree builds can be used to work around this issue.
See Install.md for instructions.

Since out of tree builds requires a clean source tree, Vagrantfile can
not be a generated file. This commit removes Vagrantfile.in, commit
Vagrantfile instead.

Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Thomas Graf <tgraf@noironetworks.com>