client: fix script execution

if __name__ == "__main__" should be first instead of try block. We want
execute it only when file was executed as script

https://fedorahosted.org/freeipa/ticket/6392

Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>

client/ipa-client-install

@@ -257,14 +257,15 @@ def main():
 
     return rval
 
-try:
-    if __name__ == "__main__":
+
+if __name__ == "__main__":
+    try:
         sys.exit(main())
-except KeyboardInterrupt:
+    except KeyboardInterrupt:
         sys.exit(1)
-except RuntimeError as e:
+    except RuntimeError as e:
         sys.exit(e)
-finally:
+    finally:
         try:
             os.remove(client.CCACHE_FILE)
         except Exception: