TT#15855 Fix shellcheck warnings for debian/ngcp-rtpengine-kernel-dkms.postinst

Change-Id: I6e6330123520bac2bfe0dfdc1305d1eb3f955457

debian/ngcp-rtpengine-kernel-dkms.postinst

@@ -5,8 +5,8 @@ set -e
 package=ngcp-rtpengine-kernel-dkms
 name=ngcp-rtpengine
 
-version=`dpkg-query -W -f='${Version}' "$package" \
-		|rev|cut -d- -f2-|rev|cut -d':' -f2|tr -d "\n"`
+version=$(dpkg-query -W -f="\${Version}" "$package" \
+		|rev|cut -d- -f2-|rev|cut -d':' -f2|tr -d "\n")
 
 
 if [ -x /usr/sbin/ngcp-virt-identify ]; then
@@ -18,13 +18,13 @@ fi
 if [ "$VIRT" = "yes" ]; then
 	echo "Container environment detected. Skip dkms"
 else
-	isadded=`dkms status -m "$name" -v "$version"`
+	isadded=$(dkms status -m "$name" -v "$version")
 	if [ "x${isadded}" = "x" ] ; then
 		dkms add -m "$name" -v "$version"
 	fi
 
 	if [ "$1" = 'configure' ] ; then
-		dkms build -m "$name" -v "$version" && dkms install -m "$name" -v "$version" || true
+		( dkms build -m "$name" -v "$version" && dkms install -m "$name" -v "$version" ) || true
 
 		# try to start the daemon
 		if [ -x /etc/init.d/ngcp-rtpengine-daemon ] ; then