fix fast reboot compatibility (#3083)

* fix fast reboot compatibility

We should handle both cases for backward-compatible with 201803:
 - fast-reboot
 - SONIC_BOOT_TYPE=fast-reboot

* handle review comments
* add a comment that getBootType code snippet is shared between two files

files/build_templates/docker_image_ctl.j2

@@ -33,15 +33,15 @@ function updateHostName()
 
 function getBootType()
 {
-    local BOOT_TYPE
+    # same code snippet in files/scripts/syncd.sh
-    case "$(cat /proc/cmdline | grep -o 'SONIC_BOOT_TYPE=\S*' | cut -d'=' -f2)" in
+    case "$(cat /proc/cmdline)" in
-    warm*)
+    *SONIC_BOOT_TYPE=warm*)
         TYPE='warm'
         ;;
-    fastfast)
+    *SONIC_BOOT_TYPE=fastfast*)
         TYPE='fastfast'
         ;;
-    fast*)
+    *SONIC_BOOT_TYPE=fast*|*fast-reboot*)
         TYPE='fast'
         ;;
     *)

files/scripts/syncd.sh

@@ -55,14 +55,15 @@ function wait_for_database_service()
 
 function getBootType()
 {
-    case "$(cat /proc/cmdline | grep -o 'SONIC_BOOT_TYPE=\S*' | cut -d'=' -f2)" in
+    # same code snippet in files/build_templates/docker_image_ctl.j2
-    warm*)
+    case "$(cat /proc/cmdline)" in
+    *SONIC_BOOT_TYPE=warm*)
         TYPE='warm'
         ;;
-    fastfast)
+    *SONIC_BOOT_TYPE=fastfast*)
         TYPE='fastfast'
         ;;
-    fast*)
+    *SONIC_BOOT_TYPE=fast*|*fast-reboot*)
         TYPE='fast'
         ;;
     *)