Update Vagrant directories in .gitignore

Vagrantfile and all related stuff moved to dev/ directory.
Then .gitignore should be updated with this change.

Change-Id: I15decd9d7ac21effe1485aead493da33002383ec
Closes-Bug: #1505079

.gitignore

@@ -25,7 +25,7 @@ ChangeLog
 doc/build
 
 # Files generated by Vagrant
-vagrant/vagrantkey
-vagrant/vagrantkey.pub
-vagrant/storage/
+dev/vagrant/vagrantkey
+dev/vagrant/vagrantkey.pub
+dev/vagrant/storage/
 .vagrant/