cubicweb #687194 cubicweb-ctl exlog : fix help message [resolved]

the help message displays 2 different usages (incompatible):

$ cubicweb-ctl exlog -h
Usage: cubicweb-ctl exlog

Examine a rql log file.

usage: python exlog.py < rql.log
...
prioritynormal
typebug
done in3.6.1
load0.000
load left0.000
closed by<not specified>