user: Update logic to check if user exists in macOS (#76592)

'dscl -list' returns 0 even if the user does not exists. This
leads to errorenous condition in user module.
Using 'dscl -read UniqueID' can return if user exists or not.

Signed-off-by: Abhijeet Kasurde <akasurde@redhat.com>

changelogs/fragments/user_mac.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+- user - update logic to check if user exists or not in MacOS.

lib/ansible/modules/user.py

@@ -2283,13 +2283,10 @@ class DarwinUser(User):
         # sys.stderr.write('*** |%s| %s -> %s\n' %  (property, out, lines))
         if len(lines) == 1:
             return lines[0].split(': ')[1]
-        else:
         if len(lines) > 2:
             return '\n'.join([lines[1].strip()] + lines[2:])
-            else:
         if len(lines) == 2:
             return lines[1].strip()
-                else:
         return None
 
     def _get_next_uid(self, system=None):
@@ -2444,7 +2441,7 @@ class DarwinUser(User):
     def user_exists(self):
         '''Check is SELF.NAME is a known user on the system.'''
         cmd = self._get_dscl()
-        cmd += ['-list', '/Users/%s' % self.name]
+        cmd += ['-read', '/Users/%s' % self.name, 'UniqueID']
         (rc, out, err) = self.execute_command(cmd, obey_checkmode=False)
         return rc == 0