Blacklist /dev/shm too.

Summary:
Apparently amazon doesn't have these other things, but does
have /dev/shm. If anyone knows where there might be an exhaustive list
of these guys...

Test Plan: pytest

Reviewers: carl, carlos, chase

Reviewed By: carl

CC: dashboard

Maniphest Tasks: T7885

Differential Revision: http://grizzly.memsql.com/D4207