Make gpinitsystem similar to gpstart and gpstop prompting (#1942)

`gpinitsystem`, `gpstart` and `gpstop` had different prompting before:

$ gpinitsystem -c gpinitsystem_config 
...
Continue with Greenplum creation **Yy/Nn>**
n
...

$ gpstart
...

Continue with Greenplum instance startup **Yy|Nn (default=N):**
**>** n
...

$ gpstop
...

Continue with Greenplum instance shutdown **Yy|Nn (default=N):**
**>** n
...

This commit makes them consistent:

$ gpinitsystem -c gpinitsystem_config 
...

Continue with Greenplum creation Yy|Nn (default=N):
> n

gpMgmt/bin/lib/gp_bash_functions.sh

@@ -913,7 +913,8 @@ CREATE_GROUP_MIRROR_ARRAY () {
 }
 
 GET_REPLY () {
-	$ECHO "$1 Yy/Nn>"
+	$ECHO -e "\n$1 Yy|Nn (default=N):"
+	$ECHO -n "> "
 	read REPLY
 	if [ -z $REPLY ]; then
 		LOG_MSG "[WARN]:-User abort requested, Script Exits!" 1