[BUG] IllegalArgumentException in BackendRole tests

[dbwiddis]

What is the bug?

Five tests fail with errors similar to:

ParseUtilsTests > testIsAdminBackendRoleIsAllAccess FAILED
    java.lang.IllegalArgumentException: No '=' present: RDKFF
        at __randomizedtesting.SeedInfo.seed([6AD829970D47720D:56C643D358E0F1AC]:0)
        at org.opensearch.commons.authuser.User.parseAttributeInfoFromCustomAttributeName(User.java:383)
        at org.opensearch.commons.authuser.User.convertCustomAttributeNamesToMap(User.java:373)
        at org.opensearch.commons.authuser.User.<init>(User.java:86)
        at org.opensearch.flowframework.util.ParseUtilsTests.testIsAdminBackendRoleIsAllAccess(ParseUtilsTests.java:434)

Tests with failures:

• org.opensearch.flowframework.util.ParseUtilsTests.testIsAdminBackendRoleIsAllAccess
• org.opensearch.flowframework.util.ParseUtilsTests.testAddUserRoleFilterWithUserBackendRole
• org.opensearch.flowframework.util.ParseUtilsTests.testIsAdmin
• org.opensearch.flowframework.util.ParseUtilsTests.testAddUserRoleFilterWithEmptyUserBackendRole
• org.opensearch.flowframework.util.ParseUtilsTests.testAddUserRoleFilterWithNullUserBackendRole

How can one reproduce the bug?

1. Check out main branch.
2. Run ./gradlew test

What is the expected behavior?

Tests pass

What is your host/environment?

Repro locally on macOS; causing failures on any new PR (such as #1234)

Do you have any additional context?

Caused by opensearch-project/common-utils#878