Update default box URL for older Vagrant installs
Update default box URL for older Vagrant installs

Hashicorp decided to clean up some HTTP redirects that are needed by all
Vagrant clients before v1.9.6. This will break setting up new installs
for a *lot* of our users. This commit attempts to work around the issue
by changing the default configuration to new expected value.

Bug: T187978
Change-Id: I3a3a52c0d75bab2e98cb6235b58d3e8b7713bb8a

wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant