SPIGOT-5362: Suspicious stews fail isSimilar check

src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaSuspiciousStew.java

@@ -223,7 +223,7 @@ public class CraftMetaSuspiciousStew extends CraftMetaItem implements Suspicious
 
     @Override
     boolean notUncommon(CraftMetaItem meta) {
-        return super.notUncommon(meta) && (meta instanceof CraftMetaPotion || isStewEmpty());
+        return super.notUncommon(meta) && (meta instanceof CraftMetaSuspiciousStew || isStewEmpty());
     }
 
     @Override

src/test/java/org/bukkit/craftbukkit/inventory/ItemMetaTest.java

@@ -405,6 +405,10 @@ public class ItemMetaTest extends AbstractTestingBase {
         final ItemStack blank = new ItemStack(Material.STONE);
         final ItemStack craftBlank = CraftItemStack.asCraftCopy(blank);
 
+        // Check that equality and similarity works for each meta implementation
+        assertThat(name, provider.stack(), is(provider.stack()));
+        assertThat(name, provider.stack().isSimilar(provider.stack()), is(true));
+
         downCastTest(name, provider.stack(), blank);
         blank.setItemMeta(blank.getItemMeta());
         downCastTest(name, provider.stack(), blank);