Fix importing of unanticipated .mjs modules in ImportScanner.
Fix importing of unanticipated .mjs modules in ImportScanner.

Should fix this problem reported by @arggh:
https://github.com/meteor/meteor/pull/10522#issuecomment-508908306

Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor