el init scripts: send errors to stderr and exit with proper return code

`exit -1` is out of range in shell scripts and returning
with 255, while init scripts are supposed to be exit with `1`
and similar on errors.

We're following
http://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/iniscrptact.html
and returning with exit code 6 for configuration issues.

Change-Id: I8eda8e059c4ea10b9ddbddd1306627894073b034

el/rtpengine-recording.init

@@ -23,8 +23,8 @@ if [ -f /etc/sysconfig/rtpengine-recording ]
 then
         . /etc/sysconfig/rtpengine-recording
 else
-	echo "Error: /etc/sysconfig/rtpengine-recording not present"
-	exit -1
+	echo "Error: /etc/sysconfig/rtpengine-recording not present" >&2
+	exit 6
 fi
 
 prog=rtpengine-recording

el/rtpengine.init

@@ -26,8 +26,8 @@ if [ -f /etc/sysconfig/rtpengine ]
 then
         . /etc/sysconfig/rtpengine
 else
-	echo "Error: /etc/sysconfig/rtpengine not present"
-	exit -1
+	echo "Error: /etc/sysconfig/rtpengine not present" >&2
+	exit 6
 fi
 
 rtpengine=/usr/sbin/rtpengine
@@ -52,8 +52,8 @@ build_opts() {
 	else
 		# configfile exists?
 		if [ ! -f "$configfile" ];then
-			echo "Error: $configfile not present"
-			exit -1
+			echo "Error: $configfile not present" >&2
+			exit 6
 		fi
 
 		# get table variable from config
@@ -64,8 +64,8 @@ build_opts() {
 
 		# error if directive is not presented in config
 		if [ -z "$table" ];then
-			echo "Error: directive table= is not present in $configfile"
-			exit -1
+			echo "Error: directive table= is not present in $configfile" >&2
+			exit 6
 		fi
 
 		# enable iptables module if derective set and positive