Description of problem:
When Content Synchronization plugin enabled, passing malformed cookie to
ldapsearch makes DS crash.

How reproducible:
always

Steps to Reproduce:
1. make a fresh install of DS
2. enable Content Synchronization plugin and Retro Changelog plugin, restart
server
3. run ldapsearch with malformed cookie
ldapsearch -h localhost:389 -D "cn=Directory Manager" -w Secret123 -LLL -b
dc=example,dc=com -E sync=ro/"#"

Actual results:
Server crashes
ldapsearch -h localhost:389 -D "cn=Directory Manager" -w Secret123 -LLL -b
dc=example,dc=com -E sync=ro/"#"
ldap_result: Can't contact LDAP server (-1)

Expected results:
Server should not crash and report that cookie is invalid, like in this
example:
ldapsearch -h localhost:389 -D "cn=Directory Manager" -w Secret123 -LLL -b
dc=example,dc=com -E sync=ro/"##"
Content Sync Refresh Required (4096)
Additional information: Invalid session cookie