Improve make_site.sh validation checks for git remotes
Improve make_site.sh validation checks for git remotes

This was using the "apache" remote and giving a confusing error when it
was not set. We'll use "origin" and do a better job of validating that
it's set.

Change-Id: I1bf22ad01706319f0e5a9a2beb99d21511393f42
Reviewed-on: http://gerrit.cloudera.org:8080/8677
Reviewed-by: Mike Percy <e07a1fd797b473a9c849e618aa2ce06d8055760b@apache.org>
Tested-by: Mike Percy <e07a1fd797b473a9c849e618aa2ce06d8055760b@apache.org>

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