Invoke callback with proper single/multi result

Change-Id: I397c7a301bc8457a78b3e7f55826a3460e00460b
Make txbasic Py3 compatible

Change-Id: I8e3164766f84cabf19e8ee4bbbf7f9c910e9269d
Remove extra print in tests

Change-Id: I3d53b3494e26da641ae0537b977aa981f85389de
txbench: Uncomment callLater for test duration

Change-Id: Ic6856c50e3cac24e27c423e3fef15f6d0fb46726