procd: update to the latest git HEAD

b8238df sysupgrade: support "backup" attribute

This update requires "sysupgrade" method callers to pass "backup"
attribute if $UPGRADE_BACKUP is used in the project.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit 9785a9121d2d7a0a25bcd2924ee78fafada056da)

package/system/procd/Makefile

@@ -12,9 +12,9 @@ PKG_RELEASE:=1
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(PROJECT_GIT)/project/procd.git
-PKG_MIRROR_HASH:=7707b4a8f010c7314441f7b0c029e7a3ba9841b354e61d7cc552fbba3b286fcc
-PKG_SOURCE_DATE:=2019-09-05
-PKG_SOURCE_VERSION:=0f3c1366bb927e483abfae23dee0d15e26f87064
+PKG_MIRROR_HASH:=ace1cb8406b91b0170afe9ba78edbeb054b6d3ca8f3976c546f71c1a1ed99be9
+PKG_SOURCE_DATE:=2019-09-11
+PKG_SOURCE_VERSION:=b8238df0fb9585b5ec9acbc0f4285dad953f2192
 CMAKE_INSTALL:=1
 
 PKG_LICENSE:=GPL-2.0