treewide: sysupgrade: pass "save_partitions" option to the "sysupgrade" method

This explicitly lets stage2 know if partitions should be preserved. No
more "touch /tmp/sysupgrade.always.overwrite.bootdisk.partmap" hack.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

package/base-files/files/sbin/sysupgrade

@@ -351,12 +351,6 @@ if [ $TEST -eq 1 ]; then
 	exit 0
 fi
 
-if [ $SAVE_PARTITIONS -eq 0 ]; then
-	touch /tmp/sysupgrade.always.overwrite.bootdisk.partmap
-else
-	rm -f /tmp/sysupgrade.always.overwrite.bootdisk.partmap
-fi
-
 install_bin /sbin/upgraded
 v "Commencing upgrade. Closing all shell sessions."
 
@@ -371,7 +365,8 @@ else
 		\"path\": $(json_string "$IMAGE"),
 		\"command\": $(json_string "$COMMAND"),
 		\"options\": {
-			\"save_config\": $SAVE_CONFIG
+			\"save_config\": $SAVE_CONFIG,
+			\"save_partitions\": $SAVE_PARTITIONS
 		}
 	}"
 fi