Set tap keepalive default to 60s.
Set tap keepalive default to 60s.

Change-Id: I9fe8a068b568c072ffaff899e08eb9c1cbfdbd05
Reviewed-on: http://review.membase.org/4020
Reviewed-by: Sean Lynch <9c3328a4a1f4f8f5c18b2d5b9057163c49b93ff3@literati.org>
Tested-by: Sean Lynch <9c3328a4a1f4f8f5c18b2d5b9057163c49b93ff3@literati.org>

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