Add depends on bind-utils for oo-diagnostics

oo-diagnostics uses the host command, which is in the bind-utils package,
so make rubygem-openshift-origin-common, which includes the oo-diagnostics
command, depend on the bind-utils package.

The above can be a problem on an OpenShift node host, where there may be no
other package installed that pulls in the bind-utils package.  On an
OpenShift broker host, the rubygem-openshift-origin-dns-nsupdate and
openshift-origin-broker-util packages will pull in the bind-utils package.

To be extra safe, add a check in prereq_domain_resolves to warn and skip
the test if the host command cannot be found.

This commit fixes bug 1058527.
nothing in the module use or requires json and mocha, so no need to have it in gemspec
Also fix the spec file for extranous Requires
Merge pull request #4599 from Miciah/bug-1058527-oo-diagnostics-is-missing-a-dependency-on-bind-utils

Merged by openshift-bot
Merge pull request #4242 from mscherer/fix/kerberos/requires

Merged by openshift-bot
Adding explanation comments for two broker configurations
Merge pull request #4669 from abhgupta/abhgupta-dev

Adding explanation comments for two broker configurations