Fix a pool lifetime issue in the ruby bindings.

* subversion/bindings/swig/svn_client.i
  (svn_client_ctx_t): Use svn_client_create_context2() instead of the
   deprecated svn_client_create_context(). Obtain a config hash from
   svn_config_get_config() and pass it to svn_client_create_context2().
  (svn_client_set_config): Copy the provided config into ctx->config.
   This ensures proper lifetime of ctx->config. For some reason the
   'config' data provided to this function had been freed by the time
   the test suite reached the svn_client_get_config() function.
   Copying the provided data into the pool of ctx->config fixes the problem.

* subversion/bindings/swig/ruby/test/test_client.rb
  (test_set_config): Don't expect ctx.config to be nil anymore after
   the context is created. It is now equal to the default configuration.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1586467 13f79535-47bb-0310-9956-ffa450edef68