Added the ability to run jeepyb not only on the host where the Gerrit installed.

In the previous version of this script jeepyb could be run
on the same host where Gerrit installed,
because in manage_projects.py was used 'localhost' directive.

The new version jeepyb can be run on any side,
because 'localhost' directive was changed to 'GERRIT_HOST'.

Change-Id: I4faa2d0877864bdaa69bc55a6bcce882faca66df