Revert "[BUGFIX] Cleanup stream after each spec run"

This reverts commit 139e5ed3772c0c62b93dfab1c766ef5366e6e035.

This resulted in doubly closing streams and therefore segfaults in Nokogiri (see https://github.com/sparklemotion/nokogiri/issues/1108) and appears not to resolve the hanging issues on JRuby any more. A better JRuby solution should be sought.