tests: replace .testr.conf with .stestr.conf

TrivialFix:In the change[1] os_testr changed under the covers
from using testr to stestr, so that we now get the following
warning:
   ostestr.py:120:
   UserWarning: No .stestr.conf file found in the CWD.
   Please create one to to replace the .testr.conf. You
   can find a script to do this in the stestr git repository.
So remove the .testr.conf and add .stestr.conf which was
generated using a utility script as documented here [2].
[1] Id7cb2a39a8308f1413608dcf19273a1d7f33592e
[2] https://media.readthedocs.org/pdf/stestr/stable/stestr.pdf

Change-Id: I9fd1dba15e2e8fbb30208f44baea0f9d69ee4b93

.gitignore

@@ -26,6 +26,7 @@ pip-log.txt
 
 # Unit test / coverage reports
 .coverage
+.stestr/*
 .tox
 nosetests.xml
 cover/*

.stestr.conf

@@ -0,0 +1,3 @@
+[DEFAULT]
+test_path=${TEST_PATH:-./qinling/tests}
+top_dir=./

.testr.conf

@@ -1,8 +0,0 @@
-[DEFAULT]
-test_command=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
-             OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
-             OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-60} \
-             OS_LOG_CAPTURE=${OS_LOG_CAPTURE:-1} \
-             ${PYTHON:-python} -m subunit.run discover -t ./ ./qinling/tests $LISTOPT $IDOPTION
-test_id_option=--load-list $IDFILE
-test_list_option=--list