teuthology/task: improve documentation of "print" internal task
The documentation is base on the commit message that first
introduced this task, but makes it clear that the arguments
will appear in teuthology.log.
"""
Print task
+
+A task that logs whatever is given to it as an argument. Can be used
+like any other task (under sequential, etc...).j
+
+For example, the following would cause the strings "String" and "Another
+string" to appear in the teuthology.log before and after the chef task
+runs, respectively.
+
+tasks:
+- print: "String"
+- chef: null
+- print: "Another String"
"""
import logging
