change client code to use specific exceptions and throw bad status if

src/ruby/lib/grpc/errors.rb

src/ruby/lib/grpc/generic/active_call.rb

src/ruby/lib/grpc/generic/service.rb

src/ruby/pb/grpc/health/checker.rb

src/ruby/pb/test/client.rb

src/ruby/spec/error_sanity_spec.rb

src/ruby/spec/generic/client_stub_spec.rb

src/ruby/spec/generic/rpc_server_spec.rb

src/ruby/spec/pb/health/checker_spec.rb