[ScriptInterpreter] Initialize globals when loading a scripting module.

The LoadScriptingModule used by command script import wasn't
initializing the LLDB global variables (things like `lldb.frame` and
`lldb.debugger`). They would get initialized however when running the
interactive script interpreter or running a single script line (e.g.
`script print(lldb.frame)`). This patch fixes that by properly
initializing the globals when loading a Python module.

Differential revision: https://reviews.llvm.org/D67644

llvm-svn: 372060