fix(tests): Introduce junit5 vintage engine for running junit4 test c…

…ases over junit5 in rosco (spinnaker#958)

Spring boot 2.4.x removed JUnit5 vintage engine from spring-boot-starter-test.
[https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.4-Release-Notes#junit-5s-vintage-engine-removed-from-spring-boot-starter-test]
It is required for executing junit4 based test cases in rosco.
So, introducing junit-vintage-engine dependency in build.gradle, using testRuntimeOnly() as suggested in section 3.1 of https://junit.org/junit5/docs/5.6.2/user-guide/index.pdf

After applying this fix, coverage increased from 217 to 252 test case executions.

rosco-web/rosco-web.gradle

@@ -63,10 +63,6 @@ dependencies {
 
 }
 
-test {
-  useJUnitPlatform()
-}
-
 ospackage {
   from('../halconfig/packer') {
     into '/opt/rosco/config/packer'