[warm-reboot] remove ISSU bank check (#2958)

### What I did

I removed issu bank check:

1. The file in which SDK holds ISSU bank information has changed and is no longer issu_bank.txt
2. We shouldn't check the SDK dump content from SONiC as that information and its format is constantly changing. Overwriting it might be risky when SONiC and SDK are out of sync regarding the format of the file
3. ISSU bank information is written by pre_shutdown request anyway. Verifying whether the information was indeed written right after that seems redundant
4. The check is made after ```set +e```, so at the moment we "detect" a problem it is already too late

#### How I did it

Removed the relevant code.

#### How to verify it

Run warm-reboot on device.

scripts/fast-reboot

@@ -193,7 +193,7 @@ function request_pre_shutdown()
 {
     if [ -x ${DEVPATH}/${PLATFORM}/${PLATFORM_REBOOT_PRE_CHECK} ]; then
         debug "Requesting platform reboot pre-check ..."
-    	${DEVPATH}/${PLATFORM}/${PLATFORM_REBOOT_PRE_CHECK} ${REBOOT_TYPE} 
+    	${DEVPATH}/${PLATFORM}/${PLATFORM_REBOOT_PRE_CHECK} ${REBOOT_TYPE}
     fi
     debug "Requesting pre-shutdown ..."
     STATE=$(timeout 5s docker exec syncd /usr/bin/syncd_request_shutdown --pre &> /dev/null; if [[ $? == 124 ]]; then echo "timed out"; fi)
@@ -202,34 +202,6 @@ function request_pre_shutdown()
     fi
 }
 
-function recover_issu_bank_file()
-{
-    debug "Recovering the (${ISSU_BANK_FILE}) file"
-    docker exec -i syncd sx_api_dbg_generate_dump.py
-    issu_bank_value=`docker exec -i syncd cat /tmp/sdkdump | grep 'ISSU Bank' | grep -o -E '[0-9]+'`
-    printf $issu_bank_value > /host/warmboot/issu_bank.txt
-}
-
-function check_issu_bank_file()
-{
-    ISSU_BANK_FILE=/host/warmboot/issu_bank.txt
-
-    if [[ ! -s "$ISSU_BANK_FILE" ]]; then
-        error "(${ISSU_BANK_FILE}) does NOT exist or empty ..."
-        recover_issu_bank_file
-        return
-    fi
-
-    issu_file_chars_count=`stat -c %s ${ISSU_BANK_FILE}`;
-    issu_file_content=`awk '{print $0}' ${ISSU_BANK_FILE}`
-
-    if [[ $issu_file_chars_count != 1 ]] ||
-        [[ "$issu_file_content" != "0" && "$issu_file_content" != "1" ]]; then
-        error "(${ISSU_BANK_FILE}) is broken ..."
-        recover_issu_bank_file
-    fi
-}
-
 function wait_for_pre_shutdown_complete_or_fail()
 {
     debug "Waiting for pre-shutdown ..."
@@ -464,7 +436,7 @@ function invoke_kexec() {
 
 function load_kernel() {
     # Load kernel into the memory
-    invoke_kexec -a 
+    invoke_kexec -a
 }
 
 function load_kernel_secure() {
@@ -630,7 +602,7 @@ fi
 if is_secureboot && grep -q aboot_machine= /host/machine.conf; then
     load_aboot_secureboot_kernel
 else
-    # check if secure boot is enable in UEFI 
+    # check if secure boot is enable in UEFI
     CHECK_SECURE_UPGRADE_ENABLED=0
     SECURE_UPGRADE_ENABLED=$(bootctl status 2>/dev/null | grep -c "Secure Boot: enabled") || CHECK_SECURE_UPGRADE_ENABLED=$?
     if [[ CHECK_SECURE_UPGRADE_ENABLED -ne 0 ]]; then
@@ -773,17 +745,9 @@ for service in ${SERVICES_TO_STOP}; do
             # Pre-shutdown syncd
             initialize_pre_shutdown
 
-            if [[ "x$sonic_asic_type" == x"mellanox" ]]; then
-                check_issu_bank_file
-            fi
-
             request_pre_shutdown
 
             wait_for_pre_shutdown_complete_or_fail
-
-            if [[ "x$sonic_asic_type" == x"mellanox" ]]; then
-                check_issu_bank_file
-            fi
         fi
 
         if [[ "$REBOOT_TYPE" = "fastfast-reboot" || "$REBOOT_TYPE" = "fast-reboot" ]]; then