tailProcessStdoutLog and tailProcessStderrLog always return all the data

[szegad]

Hi,
I've just noticed that these two RPC calls always return all the log.
A quick read through the sources pointed to options.py : tailFile: 1871 (my version is 3.1.3 - it's line 1995 in the current github version). This line causes the offset to be always negative and it's getting set to 0 in the next lines. There's someting wrong with tailFile logic.
It seems easy to fix, although I know nothing about Python ;).