Firmware probably emptying or not allowing cache

[daniele-athome]

Just catch the exception and return current system date.

java.lang.RuntimeException: expected SNTP time from last boot to be cached. couldn't find it.
       at com.instacart.library.truetime.TrueTime._getCachedSntpTime(TrueTime.java:122)
       at com.instacart.library.truetime.TrueTime.now(TrueTime.java:28)
       at org.kontalk.service.KeyPairGeneratorService$GeneratorThread.getRealtime(KeyPairGeneratorService.java:194)
       at org.kontalk.service.KeyPairGeneratorService$GeneratorThread.run(KeyPairGeneratorService.java:158)