EXAMPLES: opentracing: refined shell scripts for testing filter performance

EXAMPLES: opentracing: refined shell scripts for testing filter performance

When calling the 'basename' command, the argument ${0} is enclosed in
quotation marks.  This is necessary if the path of the executable script
(contained in that argument) has "non-standard" elements, such as space
and the like.

Also, in the script 'test-speed.sh' the function sh_exit() has been added
for easier printing of messages at the end of execution.

This patch must be backported as far as 2.4.