Correct the mongodb_replica_set option's description

Current description for mongodb_replica_set is wrong, this patch
fixes it.

Change-Id: I0121beb7a71a282eb73b48d7a7fd4dccb0d36a31
DocImpact
Fix wrong example of capabilities

Capabilities for storage is "storage:production_ready", but the
sample of Capabilities for storage is only "production_ready",
which cause wrong description in document, and misleading developers.

Change-Id: I98da1908ca99d9a20e0cbf367b73275da09f9f82
Merge "Fix wrong example of capabilities"