cannot filter desired flavor in the search box

[zhaoleilc]

Description
===========
There are 20 items per page by default in the Flavors of the horizon.
When there are a lot of flavors in the environments, we can inspect them
in different pages. However, we cannot filter desired flavor which can be
seen in another page in the search box. For example, we can filter desired
flavor in the second page rather than the first page as the desired flavor
can be seen in the second page.

Steps to reproduce
==================
1. Guarantee there are some pages of flavors.
2. There is a flavor whose flavor name is test_flavor in the second page
of the Flavors of the horizon.
3. Search the test_flavor in the first page.
4. Search the test_flavor in the second page.

Expected result
===============
Both the first page and the second page can be searched the desired flavor.

Actual result
=============
In the second page, we can get the desired flavo, while in the first page
the result is empty.

Environment
===========
either queens or rocky branch of horizon

Logs & Configs
==============
None.