more robust wait for boot (use WaitForCommunicator which is built-in action in Vagrant 1.3+.)
check Vagrant version

-use wait function in 1.3+
-alternate sleep in 1.2-

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
Remove spleep for keep behavior

Signed-off-by: Hiroshi Miura <miurahr@linux.com>