set invalid bugsnug endpoint

So that if for whatever reason bugsnug-override doesn't work (i.e. if
it fails to load and browser executing scripts), then we at least
don't send potentially critical stuff to bugsnug.

Change-Id: Ia67b27b99c1eadfc9e6edb500329ae15c09111cd
Reviewed-on: http://review.couchbase.org/38466
Reviewed-by: Pavel Blagodov <stochmail@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>