MB-23267: Prevent changing inapplicable options from cbepctl

MB-23267: Prevent changing inapplicable options from cbepctl

Check requirements in setFlushParam and setTapParam for the following
configuration parameters:

 "tap_keepalive"
 "access_scanner_enabled"
 "alog_sleep_time"
 "alog_task_time"
 "ephemeral_full_policy"

this will prevent them being set if their requirements are not met.

Change-Id: Ie70d062e5333393e12771d325d22438f5e865bdf
Reviewed-on: http://review.couchbase.org/76399
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Dave Rigby <daver@couchbase.com>