In case eventlet is installed on the system, the time.sleep() function
doesn't yield. This patch replaces time.sleep with eventlet.sleep and
thread.get_ident functions on systems with eventlet installed. With this
patch, a concurrent transaction test can be executed both with and
without eventlet successfuly.
Change-Id: I4572355d7d420111e562d4d1f4ea3dd95d4e3f7d
Related-bug: #1793499
(cherry picked from commit 64342ba52c)