Fix haveged diagnostics capture mode

[erahn]

This change resolves #9 by fixing the variable that haveged checks during the rng warmup. Previously it was checking hctxt->havege_tic but h_ctxt->havege_tics[i>>3] is what actually gets updated when in diagnostics mode. HTICK1 correctly references the right variable in both modes.

Testing was done by checking an output can be obtained:

> src/haveged -r 2 -n 100
havege_diagnostic: listening socket at 3
Writing 100  output to sample

[jirka-h]

Thanks for fixing this!