BAEL-9709 Fix start of Boot projects with parent-boot-2 parent

-Added placeholder {start-class} tag in parent-boot-2's spring-boot-maven-plugin so that any child that has a {start-class} automatically is benefited from this plugin and wil help that child class to run
-Fix startup issues of few spring boot 2 projects

parent-boot-2/pom.xml

@@ -42,6 +42,9 @@
 					<groupId>org.springframework.boot</groupId>
 					<artifactId>spring-boot-maven-plugin</artifactId>
 					<version>${spring-boot.version}</version>
+					<configuration>
+						<mainClass>${start-class}</mainClass>
+					</configuration>
 				</plugin>
 			</plugins>
 		</pluginManagement>