fix(ci): use getFullDisplayName()

Since getProjectName() is not available for all types returned from
utils.parentOrCurrentBuild(), which can result in a crash.

Signed-off-by: Jakub Sokołowski <jakub@status.im>

ci/Jenkinsfile.linux

@@ -134,7 +134,8 @@ def getArch() {
 def getE2EBuildType() {
   if (utils.isPRBuild()) { return 'prs' }
   def parent = utils.parentOrCurrentBuild()
-  if (parent != null && parent.getProjectName() == 'nightly') { return nightly }
+  if (parent == null) { return null }
+  if (parent.getFullDisplayName() =~ /nightly/) { return 'nightly' }
   return null
 }