systemd: re-enable mount propagation for udevd

With MountFlags=slave, those mounts then become private to the systemd-udevd
namespace and are no longer accessible from outside the namespace, which is
not expected

[YOCTO #8613]

(From OE-Core rev: 73f43d857fe0102033f25491007b6dbe3d5fa8ee)

(From OE-Core rev: f9c35dfc6601901664dbef2cba3a9b96bef96e64)

Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit f2092e67ea)
Signed-off-by: Alejandro Hernandez <alejandro.hernandez@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/systemd/systemd/udev-re-enable-mount-propagation-for-udevd.patch

@@ -0,0 +1,31 @@
+From: Michael Biebl <biebl@debian.org>
+Date: Sat, 27 Sep 2014 04:19:24 +0200
+Subject: udev: re-enable mount propagation for udevd
+
+Upstream-Status: Backport [http://http.debian.net/debian/pool/main/s/systemd/systemd_215-17+deb8u4.debian.tar.xz]
+
+laptop-mode-tools remounts file systems from within a udev rule to apply
+certain mount options. With MountFlags=slave, those mounts then become private
+to the systemd-udevd namespace and are no longer accessible from outside the
+namespace.
+While the root cause is the broken behaviour of laptop-mode-tools, with mount
+propagation turned off, this can result in a read-only root file system.
+Therefore revert the relevant parts from commit
+c2c13f2df42e0691aecabe3979ea81cd7faa35c7 to re-enable mount propagation for
+udevd.
+
+Once affected packages have been fixed, this patch should be dropped
+again.
+
+Closes: #762018
+diff --git a/units/systemd-udevd.service.in b/units/systemd-udevd.service.in
+index e7216d6..1e9a600 100644
+--- a/units/systemd-udevd.service.in
++++ b/units/systemd-udevd.service.in
+@@ -21,6 +21,5 @@ Sockets=systemd-udevd-control.socket systemd-udevd-kernel.socket
+ Restart=always
+ RestartSec=0
+ ExecStart=@rootlibexecdir@/systemd-udevd
+-MountFlags=slave
+ KillMode=mixed
+ WatchdogSec=1min

meta/recipes-core/systemd/systemd_219.bb

@@ -50,6 +50,7 @@ SRC_URI = "git://github.com/systemd/systemd-stable;branch=v219-stable;protocol=g
            file://00-create-volatile.conf \
            file://init \
            file://run-ptest \
+           file://udev-re-enable-mount-propagation-for-udevd.patch \
           "
 
 S = "${WORKDIR}/git"