Clarifying "ifconfig" to "ifconfig | grep '192'" in dev-hostname.js for ease of use

Summary: ifconfig | grep '192' is a more useful command than just ifconfig for the purpose of finding local IP address

Test Plan: Tested ifconfig | grep '192' and it is good for this specific purpose of finding local IP address

Reviewers: atul, ashoat

Reviewed By: atul, ashoat

Subscribers: ashoat, palys-swm, Adrian, karol-bisztyga, benschac, boristopalov

Differential Revision: https://phabricator.ashoat.com/D2545