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
- case "$(cat /proc/cmdline | grep -o 'SONIC_BOOT_TYPE=\S*' | cut -d'=' -f2)" in
- warm*)
+ # same code snippet in files/scripts/syncd.sh
+ case "$(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'
  ;;
  *)
@@ -167,7 +167,7 @@ start() {
  echo "Creating new {{docker_container_name}} container with HWSKU $HWSKU"
 {%- endif %}
 {%- if sonic_asic_platform == "mellanox" %}
- # TODO: Mellanox will remove the --tmpfs exception after SDK socket path changed in new SDK version 
+ # TODO: Mellanox will remove the --tmpfs exception after SDK socket path changed in new SDK version
 {%- endif %}
  docker create {{docker_image_run_opt}} \
 {%- if '--log-driver=json-file' in docker_image_run_opt or '--log-driver' not in docker_image_run_opt %}

files/scripts/syncd.sh

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