Remove debian java hard dependency

Give a chance to choose java version or to have multiple jdk version in the same host.

Some others java project, like leasticsearch, remove java hard dependency in debian control file.
* https://github.com/elasticsearch/elasticsearch/commit/9f43814a867b4cb348521744dcbf1004eceb64a7#diff-fb6b04e686c1b6e22755d4c7ececf443
* https://github.com/elasticsearch/elasticsearch/commit/c59b0b22e26ffcb6fed799a36e69ea92ab31f7c1#diff-fb6b04e686c1b6e22755d4c7ececf443