test(apollo-client): use assertEquals instead of assertThat

[Anilople]

What's the purpose of this PR

Fix test fail when use java 9 or above.

Which issue(s) this PR fixes:

NONE

Brief changelog

Use equals to compare properties directly.

Follow this checklist to help us incorporate your contribution quickly and easily:

• Read the Contributing Guide before making this pull request.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit tests to verify the code.
• Run mvn clean test to make sure this pull request doesn't break anything.

details

Consider code like follow

import java.util.Properties;

public class Main {

  public static void main(String[] args) {
    Properties a = new Properties();
    a.put("x", "0");

    Properties b = new Properties();
    b.put("x", "0");

    System.out.println(a.equals(b));
    System.out.println(a.entrySet().equals(b.entrySet()));
  }
}

In Jdk 8, the output will be

true
true

But in Jdk 9 or above, the output will change to

true
false

One can run it on website https://www.jdoodle.com/online-java-compiler/

So it need to compare properties directly instread of using entrySet.

[codecov-commenter]

Codecov Report

Merging #3667 (31c0500) into master (6deedb3) will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #3667      +/-   ##
============================================
+ Coverage     50.95%   50.96%   +0.01%     
- Complexity     2329     2330       +1     
============================================
  Files           449      449              
  Lines         14026    14026              
  Branches       1426     1426              
============================================
+ Hits           7147     7149       +2     
+ Misses         6392     6391       -1     
+ Partials        487      486       -1     

Impacted Files	Coverage Δ	Complexity Δ
...lo/configservice/util/InstanceConfigAuditUtil.java	74.35% <0.00%> (-1.71%)	15.00% <0.00%> (ø%)
.../apollo/internals/RemoteConfigLongPollService.java	77.10% <0.00%> (-1.21%)	28.00% <0.00%> (-1.00%)
...ervice/service/ReleaseMessageServiceWithCache.java	87.05% <0.00%> (+1.17%)	25.00% <0.00%> (+1.00%)
...ework/apollo/internals/RemoteConfigRepository.java	89.37% <0.00%> (+3.12%)	25.00% <0.00%> (+1.00%)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6deedb3...31c0500. Read the comment docs.

[nobodyiam]

LGTM