Ticket 47451 - dynamic plugins - fix crash caused by invalid
plugin config
Bug Description: After making an invalid plugin change, that should cause the
old plugin entry to be reloaded, the server will crash.
Fix Description: If a plugin fails to start after applying invalid config
changes, we need to make sure it is removed from the global
plugin lists, or else a freed plugin can be deferenced later.
Also moved the plugin validation check in dse_modify to happen
in the preop stage, so invalid configurations do not persist
in the dse.ldif
https://fedorahosted.org/389/ticket/47451
Valgrind: passed
Reviewed by: nhosoi(Thanks!)