install: make yum install more robust

If a yum install fails, try a few more times just in case it's a
transient error due to a mirror problem.
install: have node fetch key from broker until timeout

Instead of trying to download the key once and move on, the wget attempt
is repeated for a set amount of time. Once the key is downloaded it is
checked to be valid before inserting into the authorized_keys file.
install: make yum update more robust

If a yum update fails, try a few more times just in case it's a
transient error due to a mirror problem.
Merge pull request #397 from jpeeler/enterprise-2.1

Enterprise 2.1 openshift.sh installer enhancements
openshift.ks - add "EXTRA" repo vars for testing

enterprise bug 1119419
https://bugzilla.redhat.com/show_bug.cgi?id=1119419

This adds options for setting up additional repos for jbosseap,
jbossews, rhscl and rhel so we can test alpha/beta packages for channels
we depend on.
Merge pull request #423 from dobbymoodge/BZ1119419

openshift.ks - add "EXTRA" repo vars for testing
oo-install: premature restart_services

Remove unneeded RESTART_REQUIRED=true; do not want to start services
before they are configured.

Bug 1122297 - premature restart_services blocks oo-install
https://bugzilla.redhat.com/show_bug.cgi?id=1122297