Summary:
Add support for overriding os, distro and distro version to command line when inspecting system packages so one can requested see ubuntu 18.04 package from other OS.  Makes testing easier

Used shlex to shell unquote the value to be tested in the getdeps expression evaluator. getdeps expression parser didn't tolerate 18.04 as . is special char to getdeps expressions, needed to be "18.04"

Reviewed By: quark-zju

Differential Revision: D33741323

fbshipit-source-id: d83397c7fb5180a4d985d0d8ae7b3ff33b72f828