Bug 680558 - Winsync plugin fails to restrain itself to the configured subtree
    
    When an operation against an entry that is in the same database that is used
    by a sync agreement, but falls outside of the sync agreement, a message is
    logged at the fatal error level stating that the local entry could not be
    fetched.  The issue is that the sync code searches for the entry by uniqueid
    within the sync agreement scope, which fails to find the entry.  This search
    is fine, but we should not log it as a fatal message.
    
    The fix is to only log a fatal message when we fail to fetch a local entry
    that falls within the sync agreement.  This patch adds a new helper to check
    if a DN is within the sync agreement scope, which is used to determine if a
    fatal error should be logged.