tools/xl: use proper name for bash_completion file

tools/xl: use proper name for bash_completion file

Files in the bash-completion dirs should be named like the commands,
without suffix. Without this change 'xl' will not be recognized as a
command with completion support if BASH_COMPLETION_DIR is set to
/usr/share/bash-completion/completions.

Fixes: 9136a919b ("xl: Add basic bash completion for xl command.")
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>