print binlog unsafe errors at log_warnings level 1, not 2.

mysql-test/suite/binlog/r/binlog_stm_unsafe_warning.result

@@ -67,7 +67,7 @@ DROP TABLE t1;
 SET GLOBAL log_warnings = @old_log_warnings;
 # Count the number of times the "Unsafe" message was printed
 # to the error log.
-Occurrences: 0
+Occurrences: 1
 create table t1 (n1 int, n2 int, n3 int,
 key (n1, n2, n3),
 key (n2, n3, n1),

sql/sql_class.cc

@@ -6145,7 +6145,7 @@ void THD::issue_unsafe_warnings()
                           ER_BINLOG_UNSAFE_STATEMENT,
                           ER(ER_BINLOG_UNSAFE_STATEMENT),
                           ER(LEX::binlog_stmt_unsafe_errcode[unsafe_type]));
-      if (global_system_variables.log_warnings > 1 &&
+      if (global_system_variables.log_warnings > 0 &&
           !protect_against_unsafe_warning_flood(unsafe_type))
         print_unsafe_warning_to_log(unsafe_type, buf, query());
     }