Set deviceToken to null upon notification permissions acquisition failure

Summary: Set device token to null when notofications are disabled, so that it can be used to query for notification permission without the need to import react-native-notifications library.

Test Plan: This differential has no test plan. Its child diff will be used to test those changes

Reviewers: palys-swm, def-au1t, ashoat

Reviewed By: ashoat

Subscribers: ashoat, Adrian, atul, benschac, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3564