Make auto-failover common_tests work with current version.
Make auto-failover common_tests work with current version.

The config key changed from auto_failover to auto_failover_cfg.

Change-Id: Ie7a9ab9e765280f5a148532654f5c46c6c060f95
Reviewed-on: http://review.couchbase.org/7772
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

membase/ns_server,mschoch/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,daverigby/ns_server,vzasade/ns_server,nimishzynga/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,t3rm1n4l/ns_server,nimishzynga/ns_server,daverigby/ns_server,nimishzynga/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,membase/ns_server,nimishzynga/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,membase/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,mschoch/ns_server,mschoch/ns_server,vzasade/ns_server,membase/ns_server,ceejatec/ns_server,mschoch/ns_server,daverigby/ns_server