Fix stable BWC branch detection logic

This commit fixes the logic for finding the stable BWC branch. A .x
branch should only be chosen if we are testing BWC with a previous major
version.

distribution/bwc/build.gradle

@@ -56,7 +56,7 @@ if (enabled) {
   def (String major, String minor, String bugfix) = bwcVersion.split('\\.')
   def (String currentMajor, String currentMinor, String currentBugfix) = version.split('\\.')
   String bwcBranch
-  if (project.name == 'bwc-stable-snapshot') {
+  if (project.name == 'bwc-stable-snapshot' && major != currentMajor) {
     bwcBranch = "${major}.x"
   } else {
     bwcBranch = "${major}.${minor}"