oo-accept-node: Simplify find_ext_net_dev

The node runtime simply defaults to eth0 if EXTERNAL_ETH_DEV is not set,
so make oo-accept-node do the same for consistency.
oo-accept-node: Use OpenShift::Config

Use OpenShift::Config to load and parse node.conf and resource_limits.conf
for consistency with the node runtime.

Use OpenShift::Config::NODE_CONF_FILE instead of defining NODE_CONF_FILE in
oo-accept-node.

Use the new globals $CONF and $RESOURCE_LIMITS instead of ENV for storing
the settings read from node.conf and resource_limits.conf.
Unable to scale up or snapshot an app

Application.find_by_user is broken, add test and correct it.
Merge pull request #3335 from Miciah/oo-accept-node-use-Config-class

Merged by openshift-bot
Automatic commit of package [openshift-origin-cartridge-jbossews] release [0.8.2-1].
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Automatic commit of package [openshift-origin-cartridge-10gen-mms-agent] release [1.27.2-1].
Automatic commit of package [openshift-origin-cartridge-cron] release [1.11.2-1].
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Automatic commit of package [openshift-origin-cartridge-mysql] release [0.7.2-1].
Automatic commit of package [openshift-origin-cartridge-nodejs] release [1.14.3-1].
Automatic commit of package [openshift-origin-cartridge-haproxy] release [0.8.3-1].
Automatic commit of package [openshift-origin-node-proxy] release [1.11.2-1].
Automatic commit of package [openshift-origin-broker-util] release [1.13.4-1].
Automatic commit of package [rubygem-openshift-origin-common] release [1.13.3-1].
Automatic commit of package [openshift-origin-cartridge-postgresql] release [0.6.2-1].
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Automatic commit of package [openshift-origin-cartridge-ruby] release [0.8.3-1].
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