Fix stactrace with sys.reload modules.

Before this fix, sys.reload_modules would stacktrace:

[ERROR   ] An un-handled exception was caught by salt's global exception
handler:
AttributeError: 'module' object has no attribute '__context__'
Traceback (most recent call last):
  File "/home/mp/Devel/salt/scripts/salt-call", line 11, in <module>
    salt_call()
  File "/home/mp/Devel/salt/salt/scripts.py", line 95, in salt_call
    client.run()
  File "/home/mp/Devel/salt/salt/cli/__init__.py", line 353, in run
    caller.run()
  File "/home/mp/Devel/salt/salt/cli/caller.py", line 183, in run
    ret = self.call()
  File "/home/mp/Devel/salt/salt/cli/caller.py", line 101, in call
    func.__module__].__context__.get('retcode', 0)
AttributeError: 'module' object has no attribute '__context__'
Traceback (most recent call last):
  File "/home/mp/Devel/salt/scripts/salt-call", line 11, in <module>
    salt_call()
  File "/home/mp/Devel/salt/salt/scripts.py", line 95, in salt_call
    client.run()
  File "/home/mp/Devel/salt/salt/cli/__init__.py", line 353, in run
    caller.run()
  File "/home/mp/Devel/salt/salt/cli/caller.py", line 183, in run
    ret = self.call()
  File "/home/mp/Devel/salt/salt/cli/caller.py", line 101, in call
    func.__module__].__context__.get('retcode', 0)
AttributeError: 'module' object has no attribute '__context__'
Merge pull request #12474 from cachedout/sys_context

Fix stactrace with sys.reload modules.