SHDP-303 Disable distZip and buildScripts in tests

- We already have distZip task to package stuff and this collides
  with application plugin imported by boot gradle plugin. Application
  plugin creates a distZip task which calls startScripts task
  which then fails because we don't define mainClassName.
- Just need to disable startScripts and distZip tasks for spring-yarn-boot-build-tests.