Revert "Rely on consumer-info instead of checkOnline() at init time"

This reverts commit 59aee75c212669bdae4f13e8a68c568c872c722e.

See https://bugzilla.mozilla.org/show_bug.cgi?id=1014508 #c1 and #c3
Check status in checkOnline(), readyState 4 is not enough (bug 1014508)
Use mozTCPSocket to detect online/offline status (bug 1014508)
re-add support for desktop checkonline