openshift.ks: Validate settings

set_defaults: Check for unrecognized or empty settings and abort if one is found and verify that the list of components to install includes only valid components.

Example:

    # sh openshift.sh install_method=rhsm rhn_user=username rhn_password=password sm_reg_pool=pool_id broker_hostname=$host1
    Setting is assigned an empty value: CONF_BROKER_HOSTNAME
    OpenShift: Aborting Installation.
    # echo ${host1-unset}
    unset
    # sh openshift.sh install_method=rhsm rhn_user=username rhn_password=password sm_reg_pool=pool_id
    Unrecognized setting: CONF_RHN_PASSWORD
    OpenShift: Aborting Installation.
    # sh openshift.sh install_method=rhsm rhn_user=username rhn_pass=password sm_reg_pool=pool_id
    [runs to completion]
    #

RFC.