test: Upgrade "wait for virt-install" hack to non-hack

It is also needed on centos-10 now, and doesn't look the wrong thing
to do in any case.

test/check-machines-create

@@ -1328,8 +1328,8 @@ vnc_password= "{vnc_passwd}"
                     user_login = virt_install_cmd_out.split("user-login=", 1)[1].split(",")[0].rstrip()
                     self.assertIn(user_login, self.user_login)
 
-            # HACK: wait for virt-install to finish; this only races on tumbleweed
-            if self.machine.image == 'opensuse-tumbleweed' and self.create_and_run:
+            # wait for virt-install to finish
+            if self.create_and_run:
                 self.machine.execute(f"while {virt_install_cmd}; do sleep 1; done", timeout=300)
 
         def fill(self):