Allow DO to access bookkeeping information about its own actions

The getLastSecurityLogRetrievalTime(), getLastBugReportRequestTime()
and getLastNetworkLogRetrievalTime() methods are meant to be used by
system code. However, there is no harm in allowing the DO to access the
information they return - because it is information about actions that
the DO itself took.

The advantage of opening up these methods to the DO is that we can
CTS-test them.

Bug: 32692748
Test: DevicePolicyManager unit test + CTS test in separate CL

Change-Id: I1470fca2a82b9955f7aed5e8b50220bea8b56fc9