HHH-19701 add 'if exists' to 'drop sequence' on Maria

second try - thanks @WolfgangHG

Author: gavinking

hibernate-core/src/main/java/org/hibernate/dialect/sequence/MariaDBSequenceSupport.java

@@ -35,6 +35,11 @@ public String getSelectSequencePreviousValString(String sequenceName) throws Map
 		return "previous value for " + sequenceName;
 	}
 
+	@Override
+	public String getDropSequenceString(String sequenceName) throws MappingException {
+		return "drop sequence if exists " + sequenceName;
+	}
+
 	@Override
 	public boolean sometimesNeedsStartingValue() {
 		return true;