Merge from Widevine repo of http://go/wvgerrit/103107 When an offline license is reloaded, if it does not have a usage entry to indicate when the rental clock was started, the start time defaults to 0 in the ODK library (in OEMCrypto). This CL changes the code to start the rental clock in this case. It does this by signing a dummy message, which triggers the ODK library to start the rental clock. Bug: 161585265 Bug: 161023174 Test: GTS tests. http://go/forrest-run/L55100000642199761 Change-Id: I4cf555b2fb43009ffb62e7b2c1a37265c3f70bfe