Remove some instances of invalid dereferencing of local
JNI object references in JavaHL.

[in subversion/bindings/javahl/native]
* RemoteSession.cpp (RemoteSession::open):
   Do not dereference jstring parameters. Remove the now unused
   local variable 'env'.
* RemoteSessionContext.cpp (RemoteSessionContext::activate):
   Do not dereference the jobject parameter.
* org_apache_subversion_javahl_util_ConfigImpl_Category.cpp
  (ImplContext::ImplContext): Do not dereference jstring parameters.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1605720 13f79535-47bb-0310-9956-ffa450edef68