Check for 'hostmaster' using root and URI, not just "profile"

The latest provision is causing upgrades to DevShop to fail, and I FINALLY figured out why!

if (d()->profile != 'hostmaster') {

}

Since some of us extend Aegir by using our own drupal profile, we cannot check against d()->profile.

I dealt with a similar issue in #2704291: Verify of a site with function "hosting_get_features" overwrites the `~/.drush/drushrc.php` file..

Instead, let's check that the root and URI match those for @hostmaster alias. That was we can be absolutely sure we dealing with the "@hostmaster" site.

if (!(d()->root == d('@hostmaster')->root && d()->uri == d('@hostmaster')->uri)) {

}