Disable RocksDB tests that fail regularly on buildbot (MDEV-12474)

Tests which fail on Xenial fulltest

Author: elenst

storage/rocksdb/mysql-test/rocksdb/t/disabled.def

@@ -66,3 +66,8 @@ bloomfilter : MDEV-12474 Regularly fails on buildbot
 
 compact_deletes: MDEV-12663 : rocksdb.compact_deletes times out and causes other tests to fail
 
+col_opt_not_null : MDEV-12474 - Fails in fulltest
+col_opt_null : : MDEV-12474 - Fails in fulltest
+col_opt_unsigned : MDEV-12474 - Fails in fulltest
+col_opt_zerofill : MDEV-12474 - Fails in fulltest
+type_float : MDEV-12474 - Fails in fulltest