Expose underlying clock in CThreadInterrupt

Overloading sleep_for is not needed, as

* seconds and minutes can be converted to milliseconds by the compiler,
  not needing a duration_cast
* std::condition_variable::wait_for will convert milliseconds to the
  duration type of the underlying clock

So simply expose the clock.

ci/test/06_script_b.sh

@@ -47,6 +47,7 @@ if [ "${RUN_TIDY}" = "true" ]; then
           " src/rpc/fees.cpp"\
           " src/rpc/signmessage.cpp"\
           " src/test/fuzz/txorphan.cpp"\
+          " src/threadinterrupt.cpp"\
           " src/util/bip32.cpp"\
           " src/util/bytevectorhash.cpp"\
           " src/util/error.cpp"\