Add ceilometer client in devstack

Ceilometer client CLI is helpful to develop ceilometer related code. Add
it to devstack also involve more developer to use it.

Change-Id: I4147e50c00cb520ec15d63a0c34524ba8cb6654f
Signed-off-by: Yunhong, Jiang <yunhong.jiang@intel.com>
Create signing_dir for ceilometer.

Create and initialize the signing_dir for ceilometer keystone
authentication. This ensures the ceilometer to use its own PKI cache
directory for authentication and avoids the authentication error due to
the invalid cached certifications.

Change-Id: I6fbc364695ae9be800245d14fd8945d531679550
Merge "Add ceilometer client in devstack"
Merge "Create signing_dir for ceilometer."