Summary: Bringing the pkd CPU usage fix to open source releases. Now when idb is installed, Flipper will always use it to check for devices, and only fallback to instruments if not. Fixes https://github.com/facebook/flipper/issues/1028 Reviewed By: passy Differential Revision: D23293675 fbshipit-source-id: 6ff3e89167f5f6d4130f197b2a675202334d0e7d