Updating jsch.agentproxy 0.0.7 -> 0.0.8

New version uses net.java.dev.jna:jna 4.1.0. The old version uses 3.4.0,
which is only LGPL-licensed.

Reverts https://github.com/jclouds/jclouds/commit/53fc568743bb13a0001223b6c5f5cc549627296e, but if we want to be consistent with Karaf we need to wait for the result of [SMX4-1859](https://issues.apache.org/jira/browse/SMX4-1859) to be published:

http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22org.apache.servicemix.bundles.jsch-agentproxy-sshj%22