utils: ForwardServlet: fix generic forward to use path info

requestURI is no good as we may need to forward into different uris.

cleanup serlvet initialization.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=961677
Change-Id: I7307d57792fb966c8acb6ac0bdcad9302c0e3a65
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>