Fix flakiness due to indeterminate HashMap orderings in unit test

[kaiyaok2]

Description
Several (11 in total) flaky tests are found using Nondex when running commands
mvn edu.illinois:nondex-maven-plugin:1.1.2:nondex under scimono-client directory. All test flakinesses are due to the function ResourcePageQuery.apply(), which uses the default iterator of a HashMap.entrySet() when iterating through entries of the HashMap queryParams. However, an entry set for a normal HashMap is an unordered set, so it does not preserve element orders. As a result, the query parameters may not be retrieved in insertion order. This can lead to unexpected resultant URL, failure to get a PagedByIdentitySearchResult from a SCIMResponse, etc.
For example, consider testCreateCustomIdentityFilter() in ResourcePageQueryTest.java , the String resultRequestPath can be http://localhost:7070/idds/scim/v2/Users?startId=00000000-0000-1000-9000-000000000000&count=50 in one run and then http://localhost:7070/idds/scim/v2/Users?count=50&startId=00000000-0000-1000-9000-000000000000 in another.
For another example, testReadGroupsWithIndexPagedResponse() in GroupRequestTest.java may occasionally throw an javax.ws.rs.WebApplicationException after executing line 214 for the same reason.

Reasons for Fixing
These unit tests may fail nondeterministically when been run in a different OS or when using older / future versions of Java.

Fixes
Using LinkedHashMap instead of HashMap to ensure determinate iteration order.

[cla-assistant]

All committers have signed the CLA.