[users] Fix tests for setting shell

- The EXPECT_FAIL value "Abort" stops the test (I wanted 'if this
  unexpectedly passes, raise an error' -- should have read the
  documentation more closely).
- Set the shell in the config object, not just in GS.

src/modules/users/Config.cpp

@@ -100,12 +100,17 @@ Config::setUserShell( const QString& shell )
         cWarning() << "User shell" << shell << "is not an absolute path.";
         return;
     }
-    // The shell is put into GS because the CreateUser job expects it there
+    if ( shell != m_userShell )
+    {
+        m_userShell = shell;
+        emit userShellChanged(shell);
+        // The shell is put into GS as well.
         auto* gs = Calamares::JobQueue::instance()->globalStorage();
         if ( gs )
         {
             gs->insert( "userShell", shell );
         }
+    }
 }
 
 static inline void

src/modules/users/Tests.cpp

@@ -74,9 +74,7 @@ UserTests::testGetSet()
         QCOMPARE( c.userShell(), sh + sh );
 
         const QString badsh( "bash" );  // Not absolute, that's bad
-        c.setUserShell( badsh );
+        c.setUserShell( badsh );  // .. so unchanged
-        QEXPECT_FAIL( "", "Shell Unchanged", Abort );
-        QCOMPARE( c.userShell(), badsh );
         QCOMPARE( c.userShell(), sh + sh );  // what was set previously
 
         // Explicit set to empty is ok