Update to Spring Boot 1.5.15. Fixes #11043. Fixes #11032

Author: jameskleeh

build.gradle

@@ -48,7 +48,7 @@ ext {
     slf4jVersion = "1.7.25"
 
     spockVersion = '1.1-groovy-2.4'
-    springBootVersion = "1.5.14.RELEASE"
+    springBootVersion = "1.5.15.RELEASE"
     springLoadedVersion = "1.2.8.RELEASE"
     directoryWatcherVersion = "0.3.0"
     springLoadedCommonOptions = "-Xverify:none -Dspringloaded.synchronize=true -Djdk.reflect.allowGetCallerClass=true"