Fix pinnedServerCertificate not getting retained
Fix pinnedServerCertificate not getting retained

CBLReplicatorConfiguration.pinnedServerCertificate is Core Foundation type so explicitly retaining and releasing are required.

couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios