Add userdata checks to rollback cts tests

Make use of InstallUtils.processUserData to ensure that userdata
backup and restore happens correctly in the case of staged
installs.

Test: atest CtsRollbackManagerHostTestCases
Test: atest RollbackManagerTest
Bug: 134035054
Change-Id: I3428713f7955a4f97f81cc6e466eaf0993622ddd