MT#55283 dkms.prerm: do not act on daemon or module in a container

in a container
- the daemon is not started by rtpengine-kernel-dkms.postinst
- do not attempt to unload a module from the host kernel

Ref: https://bugs.debian.org/1101804
Change-Id: Id9b9184c52e1be82d47a6b89780bf594d4d5a5a9
(cherry picked from commit 4f716cf2bf)
(cherry picked from commit a85dd72cd1)

debian/ngcp-rtpengine-kernel-dkms.prerm

@@ -2,10 +2,20 @@
 
 set -e
 
-# make sure it's not running
-if [ -x /etc/init.d/ngcp-rtpengine-daemon ] ; then
-	invoke-rc.d ngcp-rtpengine-daemon stop || true
-	rmmod "xt_RTPENGINE" 2>/dev/null || true
+if [ -x "$(command -v ngcp-virt-identify)" ]; then
+	if ngcp-virt-identify --type container; then
+		VIRT="yes"
+	fi
+fi
+
+if [ "$VIRT" = "yes" ]; then
+	echo "Container environment detected. Skip daemon"
+else
+	# make sure it's not running
+	if [ -x /etc/init.d/ngcp-rtpengine-daemon ] ; then
+		invoke-rc.d ngcp-rtpengine-daemon stop || true
+		rmmod "xt_RTPENGINE" 2>/dev/null || true
+	fi
 fi
 
 #DEBHELPER#