Replace apache-commons-codec with apache-commons-codec-eap6

the apache-commons-codec conflicts with jakarta-commons-codec,
which is an older version of itself.  The eap6 build is installed
into a separate directory, so conflicts shoudln't be a problem.
Merge pull request #636 from candlepin/ckozak/commons_codec_eap6

Replace apache-commons-codec with apache-commons-codec-eap6