Append extra space after command in bash_completion

Unlike NovaClient or other Clients in OpenStack, 
there is no space append after command in Heat Client.
That means if I try to run 'heat stack-delete', I have 
to manually append the space and then append the thing 
I want to delete.
This correction will help Heat Client to be more 
convenient for operators.

Change-Id: I229653f0a1ecc2794cdb8006c22a70882084d7e1
Merge "Append extra space after command in bash_completion"