initscripts: check if swapon/swapoff exists before executing them

Not all built images contain swapon/swapoff, for instance, it is
configurable with or without them in busybox. So it'd better to check if
they exist or not before executing them.

Redirecting the potential errors to /dev/null is not good enough, which
might suppress the *real* errors.

(From OE-Core rev: 2cb1142710cc2beb762c4c2b8edd44d3a97dafa0)

Signed-off-by: Ming Liu <peter.x.liu@external.atlascopco.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/initscripts/initscripts-1.0/checkroot.sh

@@ -69,7 +69,7 @@ fi
 # before fsck, since fsck can be quite memory-hungry.
 #
 test "$VERBOSE" != no && echo "Activating swap"
-swapon -a 2> /dev/null
+[ -x /sbin/swapon ] && swapon -a
 
 #
 # Check the root filesystem.

meta/recipes-core/initscripts/initscripts-1.0/mountall.sh

@@ -33,7 +33,7 @@ kill -USR1 1
 # Execute swapon command again, in case we want to swap to
 # a file on a now mounted filesystem.
 #
-swapon -a 2> /dev/null
+[ -x /sbin/swapon ] && swapon -a
 
 : exit 0
 

meta/recipes-core/initscripts/initscripts-1.0/umountfs

@@ -12,7 +12,7 @@
 PATH=/sbin:/bin:/usr/sbin:/usr/bin
 
 echo "Deactivating swap..."
-swapoff -a
+[ -x /sbin/swapoff ] && swapoff -a
 
 # We leave /proc mounted.
 echo "Unmounting local filesystems..."