MB-100: don't crash compaction_daemon on unknown config field
MB-100: don't crash compaction_daemon on unknown config field

Which complicates adding new compaction setting fields

Change-Id: Ie12267eefac91b5dbf82f7ee74317fdbc7e5fe60
Reviewed-on: http://review.couchbase.org/27858
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

nimishzynga/ns_server,ceejatec/ns_server,nimishzynga/ns_server,mschoch/ns_server,membase/ns_server,vzasade/ns_server,membase/ns_server,mschoch/ns_server,mschoch/ns_server,daverigby/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,mschoch/ns_server,mschoch/ns_server,membase/ns_server,membase/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,daverigby/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,daverigby/ns_server,membase/ns_server,vzasade/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,membase/ns_server,mschoch/ns_server,daverigby/ns_server,nimishzynga/ns_server,ceejatec/ns_server,nimishzynga/ns_server,daverigby/ns_server