Updating task execution id next val to use sequence for sqlserver

resolves TASK-782

Updated PR to resolve issue when no task tables exist

Updated PR based on review comments.
This does not include updated tests.
This resolves a problem where task would fail because the incrementer selection occured before the tables were created.

Added unit test for SqlServerSequenceIncrementer

updated based on code review

spring-cloud-task-core/src/test/java/org/springframework/cloud/task/repository/support/SqlServerSequenceMaxValueIncrementerTests.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2020-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.task.repository.support;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class SqlServerSequenceMaxValueIncrementerTests {
+
+	private ConfigurableApplicationContext context;
+
+	@AfterEach
+	public void tearDown() {
+		if (this.context != null) {
+			this.context.close();
+		}
+	}
+
+	@Test
+	public void testDefaultDataSourceConfiguration() throws Exception {
+		this.context = new AnnotationConfigApplicationContext(
+			TaskExecutionDaoFactoryBeanTests.DefaultDataSourceConfiguration.class);
+
+		DataSource dataSource = this.context.getBean(DataSource.class);
+
+		SqlServerSequenceMaxValueIncrementer incrementer = new SqlServerSequenceMaxValueIncrementer(dataSource, "foo");
+		assertThat(incrementer.getSequenceQuery()).isEqualTo("select next value for foo");
+		assertThat(incrementer.getIncrementerName()).isEqualTo("foo");
+	}
+}