Ticket #48146 - async simple paged results issue; log pr index
    
    Description: When the request is a simple paged results search,
                 log pr index in the access log.
    Sample access log for "getent netgroup <name>":
      [..] conn=23 op=521 SRCH base="cn=accounts,dc=testrelm,dc=test" scope=2 filter="(&(|(memberOf=ipaUniqueID=3036b6a0-ee18-11e4-b7dd-00215e2032c0,cn=ng,cn=alt,dc=testrelm,dc=test))(objectClass=ipaHost))" attrs="objectClass cn fqdn serverHostName memberOf ipaSshPubKey ipaUniqueID"
      [..] conn=23 op=521 RESULT err=0 tag=101 nentries=200 etime=0 notes=P pr_idx=3
    
    (cherry picked from commit 0bff700c0a50f26819f203772085e440a1fa8c23)