common: Support loading config files from /etc

This is quite simple in fact: just added another loop to read
config files from /etc/kdumpst.d/ - /etc takes precedence over
/usr/share, like most of config files found in the field (/etc
is usually the way for users to customize something).

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>

common.sh

@@ -11,10 +11,17 @@ load_kdumpst_config() {
 			HAVE_CFG_FILES=1
 		fi
 	done
+
+	for cfg in "/etc/kdumpst.d"/*; do
+		if [ -f "$cfg" ]; then
+			. "$cfg"
+			HAVE_CFG_FILES=1
+		fi
+	done
 	shopt -u nullglob
 
 	if [ ${HAVE_CFG_FILES} -eq 0 ]; then
-		logger "kdumpst: no config files in /usr/share/kdumpst.d/ - aborting."
+		logger "kdumpst: no config files in /usr/share/kdumpst.d/ or /etc/kdumpst.d/ - aborting."
 		exit 1
 	fi
 }