DBDPersist takes On or Off

reported by Phil Endecott
note odd DBDPersist format in 2.2.0 and 2.2.1


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@569109 13f79535-47bb-0310-9956-ffa450edef68