spec: Only add apache user to the icingacmd group if existing.

Refs #5263

Conflicts:
	Changelog

icinga.spec

@@ -365,12 +365,19 @@ fi
 
 %pre gui
 # Add apacheuser in the icingacmd group
+# If the group exists, add the apacheuser in the icingacmd group.
+# It is not neccessary that icinga-cgi is installed on the same system as
+# icinga 1.x and only on systems with icinga installed the icingacmd
+# group exists.
+getent group icingacmd > /dev/null
+
+if [ $? -eq 0 ]; then
 %if "%{_vendor}" == "suse"
   %{_sbindir}/usermod -G icingacmd %{apacheuser}
 %else
   %{_sbindir}/usermod -a -G icingacmd %{apacheuser}
 %endif
-
+fi
 
 %post idoutils-libdbi-mysql