MB-100: increased default autofailover timeout to 2 minutes

Because it turns out many folks dont have environments that can
reliably avoid false positives with 30 seconds.

Change-Id: I4119a31b29a0a647628a6d0957ae478b0dc90662
Reviewed-on: http://review.couchbase.org/30905
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>