MB-5402: avoid system_stats_collector crashing other services
MB-5402: avoid system_stats_collector crashing other services

System stats gathering is a cool thing. But MB-5402 points out that
sometimes we want to count some stats quite before
system_stats_collector configured ets table for stats. We're just
ignoring any exceptions from trying to update those stats now.

Change-Id: Ifd6b0a0e985e8213a0cfc12090fe6beb7df24607
Reviewed-on: http://review.couchbase.org/16632
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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