Merge pull request #28 from thin-edge/fix-install-file-not-found-message

fix(install): check if systemd service definition exists first

src/packaging/postinstall

@@ -62,10 +62,12 @@ fi
 
 # newer monit service definitions are sometimes too strict on the "hardening" of the service
 # which results in the "tedge reconnect c8y" command failing.
-if grep -q "CapabilityBoundingSet=" /usr/lib/systemd/system/monit.service; then
-    if [ ! -e /etc/systemd/system/monit.service ]; then
-        echo "Using custom monit.service definition with custom capabilities set"
-        ln -sf /usr/share/tedge-monit-setup/service/monit.service /etc/systemd/system/monit.service
+if [ -f /usr/lib/systemd/system/monit.service ]; then
+    if grep -q "CapabilityBoundingSet=" /usr/lib/systemd/system/monit.service; then
+        if [ ! -e /etc/systemd/system/monit.service ]; then
+            echo "Using custom monit.service definition with custom capabilities set"
+            ln -sf /usr/share/tedge-monit-setup/service/monit.service /etc/systemd/system/monit.service
+        fi
     fi
 fi