[krillin] NetworkTime is available when no SIMs are inserted and modems online

Device: krillin with no SIMs inserted
Channel, Image: ubuntu-rtm/14.09-proposed, #169

While working on test scripts for the SIM sub-section of the ofono test plan I had to quirk the verification of the modem's 'Interfaces' property, which indicates which ofono interfaces are available at any given moment.

On krillin, "org.ofono.NetworkTime" is available even when there are no SIMs present. As a phone in this state can only be used for emergency calls and the phone will not auto-register to a network, it shouldn't be possible for NITZ messages to be received. For this reason, "NetworkTime" shouldn't be available if no SIMs are present.

The test cases in question are the first four in the SIM sub-section of the test plan:

https://wiki.ubuntu.com/Process/Merges/TestPlans/ofono/SIM

The tests themselves can be found in the following pull request. The code in question is in the simtestutil.py module, in the function validate_modem_properties():

https://github.com/rilmodem/ofono/pull/136