run-tree-smoketest: create a tmpdir to use with Ansible

The 'smoketest' job was failing while running the sanity test because
it was unable to copy a file from the host under test to the host
running the playbook.  The error message suggested to use a temp
directory under `/tmp` as a mitigation.

This creates a random temp directory and sets an env var to tell
Ansible to use said temp directory.

centos-ci/run-tree-smoketest

@@ -32,6 +32,25 @@ head=$(vm_cmd ostree rev-parse centos-atomic-host/7/x86_64/devel/continuous)
 
 export ANSIBLE_HOST_KEY_CHECKING=False
 
+# The 'smoketest' job was failing while trying to copy files from the host
+# under test to the host running Ansible.  The following error was observed:
+#
+#   Authentication or permission failure. In some cases, you may have been
+#   able to authenticate and did not have permissions on the target directory.
+#   Consider changing the remote tmp path in ansible.cfg to a path rooted
+#   in "/tmp". Failed command was: ( umask 77 &&
+#   mkdir -p "` echo /root/.ansible/tmp/ansible-tmp-1527796579.81-233460530664079 `" &&
+#   echo ansible-tmp-1527796579.81-233460530664079="`
+#   echo /root/.ansible/tmp/ansible-tmp-1527796579.81-233460530664079 `" ),
+#   exited with result 1
+#
+# In attempt to workaround this, we can create a temporary directory and
+# have Ansible use that.  See:
+#
+#  https://docs.ansible.com/ansible/latest/reference_appendices/config.html#default-local-tmp
+#
+export ANSIBLE_LOCAL_TEMP=$(mktemp -d)
+
 pass=0
 if ansible-playbook -v -i $ip, -u root \
     atomic-host-tests/tests/improved-sanity-test/main.yml; then