Add las126 to common role

(cherry picked from commit 56bd3290)

hosts

 # stable
 [clients]
+las93.las.kit.edu
 las113.las.kit.edu
 las115.las.kit.edu
 las116.las.kit.edu
@@ -7,7 +8,7 @@ las117.las.kit.edu
 las118.las.kit.edu
 las120.las.kit.edu
 las122.las.kit.edu
-las93.las.kit.edu
+las126.las.kit.edu
 las-gethmann.las.kit.edu
 
 [desktop]