Backport PR #5805: fix engine startup files

engine startup_file and startup_command are ignored in 2.0

closes  #5801

IPython/parallel/apps/ipengineapp.py

@@ -320,16 +320,19 b' class IPEngineApp(BaseParallelApplication):'
         
         exec_lines = []
         for app in ('IPKernelApp', 'InteractiveShellApp'):
-            if '%s.exec_lines' in config:
-                exec_lines = config.IPKernelApp.exec_lines = config[app].exec_lines
+            if '%s.exec_lines' % app in config:
+                exec_lines = config[app].exec_lines
                 break
         
         exec_files = []
         for app in ('IPKernelApp', 'InteractiveShellApp'):
-            if '%s.exec_files' in config:
-                exec_files = config.IPKernelApp.exec_files = config[app].exec_files
+            if '%s.exec_files' % app in config:
+                exec_files = config[app].exec_files
                 break
         
+        config.IPKernelApp.exec_lines = exec_lines
+        config.IPKernelApp.exec_files = exec_files
+        
         if self.startup_script:
             exec_files.append(self.startup_script)
         if self.startup_command: