[scripts]: Fix issues with checking status of the DB. Use one approach everywhere.

files/build_templates/docker_image_ctl.j2

@@ -10,11 +10,8 @@ function postStartAction()
 {%- if docker_container_name != "database" %}
     :
 {%- else %}
-    while true; do
-        if [[ "$(docker exec -i database redis-cli ping)" =~ PONG.* ]]; then
-            break
-        fi
-        sleep 1
+    until [[ $(/usr/bin/docker exec database redis-cli ping | grep -c PONG) -gt 0 ]]; do
+      sleep 1;
     done
 {%- endif %}
 {%- if docker_container_name == "snmp" %}

files/build_templates/swss.service.j2

@@ -17,7 +17,7 @@ After=nps-modules-3.16.0-4-amd64.service
 [Service]
 User=root
 # Wait for redis server start before database clean
-ExecStartPre=/bin/bash -c "while true; do if [ \"$(/usr/bin/docker exec database redis-cli ping)\" == \"PONG\" ]; then break; fi; sleep 1; done"
+ExecStartPre=/bin/bash -c 'until [[ $(/usr/bin/docker exec database redis-cli ping | grep -c PONG) -gt 0 ]]; do sleep 1; done'
 ExecStartPre=/usr/bin/docker exec database redis-cli -n 0 FLUSHDB
 ExecStartPre=/usr/bin/docker exec database redis-cli -n 1 FLUSHDB
 ExecStartPre=/usr/bin/docker exec database redis-cli -n 2 FLUSHDB

files/scripts/configdb-load.sh

@@ -1,11 +1,8 @@
 #!/usr/bin/env bash
 
 # Wait until redis starts
-while true; do
-    if [ `redis-cli ping` == "PONG" ]; then
-        break
-    fi
-    sleep 1
+until [[ $(redis-cli ping | grep -c PONG) -gt 0 ]]; do
+  sleep 1;
 done
 
 # If there is a config db dump file, load it