Don't print out "script" results twice.

We now properly detect when a result object has an immediate output stream and don't echo the results a second time.

<rdar://problem/15954906>



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@200882 91177308-0d34-0410-b5e6-96231b3b80d8