MB-7685: Remove concurrency related parameters from couchstore

Thes parameters will be decided at a higher level in the future
so it doesn't make sense to have them anymore. I am also not
aware of anyone who would want to use them or does currently
use them.

Change-Id: I117fe499dac868352084854ae1cdad992971be76
Reviewed-on: http://review.couchbase.org/24878
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>