Use os.path.join to form the cli command

 * If cli_dir path has no trailing "/" the generated command would no
 longer be malformed

 * Fix tempest.conf.sample: CLI group should not be capitalized

Change-Id: I4d367d4b6cde492ceb224c4b644d4853181a62ce
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index db6a7bd..bc191d8 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -332,8 +332,8 @@
 # ssh username for the image file
 ssh_user = cirros
 
-[CLI]
+[cli]
 # Enable cli tests
 enabled = True
 # directory where python client binaries are located
-cli_dir = /usr/local/bin/
+cli_dir = /usr/local/bin
diff --git a/tempest/cli/__init__.py b/tempest/cli/__init__.py
index 413990d..75267cf 100644
--- a/tempest/cli/__init__.py
+++ b/tempest/cli/__init__.py
@@ -16,6 +16,7 @@
 #    under the License.
 
 import logging
+import os
 import shlex
 import subprocess
 
@@ -99,7 +100,7 @@
     def cmd(self, cmd, action, flags='', params='', fail_ok=False,
             merge_stderr=False):
         """Executes specified command for the given action."""
-        cmd = ' '.join([CONF.cli.cli_dir + cmd,
+        cmd = ' '.join([os.path.join(CONF.cli.cli_dir, cmd),
                         flags, action, params])
         LOG.info("running: '%s'" % cmd)
         cmd = shlex.split(cmd)