Ensure /etc/rc.local to be executable

Summary:
When rebooting Eglide, a Debian instance, the console reported
not to be able to execute /etc/rc.local as it's not executable.

Test Plan: /etc/rc.local

Reviewers: Sandlayth

Reviewed By: Sandlayth

Differential Revision: https://devcentral.nasqueron.org/D2585