Actually make the fast code path return early for Aligner.align (#7222)

* Actually make the fast code path return early

* Totally avoid any kind of copy

* Revert "Totally avoid any kind of copy"

This reverts commit b528234.

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

xarray/core/alignment.py

@@ -551,6 +551,7 @@ def align(self) -> None:
             # fast path for the trivial case
             (obj,) = self.objects
             self.results = (obj.copy(deep=self.copy),)
+            return
 
         self.find_matching_indexes()
         self.find_matching_unindexed_dims()