shaded client includes several non-relocated third party dependencies

<!-- markdown --> The HBase shaded artifacts (hbase-shaded-client and hbase-shaded-server) no longer contain several non-relocated third party dependency classes that were mistakenly included. Downstream users who relied on these classes being present will need to add a runtime dependency onto an appropriate third party artifact. Previously, we erroneously packaged several third party libs without relocating them. In some cases these libraries have now been relocated; in some cases they are no longer included at all. Includes: * jaxb * jetty * jersey * codahale metrics (HBase 1.4+ only) * commons-crypto * jets3t * junit * curator (HBase 1.4+) * netty 3 (HBase 1.1) * mokito-junit4 (HBase 1.1) There is now testing to ensure that the shaded artifacts only contain expected relocated content. It can be run via `mvn -Dtest=noUnitTests -pl hbase-shaded/hbase-shaded-check-invariants -am -Prelease verify`. For version 2.0+ this patch removes hadoop-mapreduce-client-core from the set of dependencies included for the hbase-client and hbase-shaded-client artifacts. For 2.0+, the slf4j-log4j12 dependency is now optional for both shaded artifacts.