Use OPENSHIFT_*_DIR in standalone.conf

In the JBoss cartridges' standalone.conf file, use OPENSHIFT_JBOSSAS_DIR
or OPENSHIFT_JBOSSEAP_DIR as appropriate to set the value of CART_DIR.
Bug 989831 - Fix incorrect variable.
Bug 989765 - Fix output when old jboss not present in alternatives

https://bugzilla.redhat.com/show_bug.cgi?id=989765

alternatives --remove sends output to stderr if the requested
alternative to be removed doesn't exist.  Test for existence of
alternative before trying to remove it.

Also, if uninstall, cleanup the jbossas-7 alternative
Merge pull request #3055 from Miciah/update-CART_DIR-in-standalone.conf

Merged by openshift-bot
Merge pull request #3226 from rmillner/BZ989831

Merged by openshift-bot
Merge pull request #3220 from detiber/bz989765

Merged by openshift-bot