Simplify logic in Spec.normalize()

lib/spack/spack/spec.py

@@ -2183,13 +2183,13 @@ def normalize(self, force=False):
         if not self.name:
             raise SpecError("Attempting to normalize anonymous spec")
 
-        if self._normal and not force:
-            return False
-
-        # avoid any assumptions about concreteness when forced
+        # Set _normal and _concrete to False when forced
         if force:
             self._mark_concrete(False)
 
+        if self._normal:
+            return False
+
         # Ensure first that all packages & compilers in the DAG exist.
         self.validate_or_raise()
         # Get all the dependencies into one DependencyMap