perf completion: Update __ltrim_colon_completions

The function is taken from the bash-completion package; update it to use
the latest version where colon_word doesn't miss quoting.
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1372941691-14684-3-git-send-email-artagnon@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/bash_completion

@@ -11,7 +11,7 @@ __ltrim_colon_completions()
 {
 	if [[ "$1" == *:* && "$COMP_WORDBREAKS" == *:* ]]; then
 		# Remove colon-word prefix from COMPREPLY items
-		local colon_word=${1%${1##*:}}
+		local colon_word=${1%"${1##*:}"}
 		local i=${#COMPREPLY[*]}
 		while [[ $((--i)) -ge 0 ]]; do
 			COMPREPLY[$i]=${COMPREPLY[$i]#"$colon_word"}