Remove hardcoded FLOPPY_DEV in helper

Check the cmdline of the kernel to determine what device to check
for find the rules file

snf-image-helper/common.sh

@@ -62,15 +62,17 @@ prepare_helper() {
 	read -a cmdline	 < /proc/cmdline
 	for item in "${cmdline[@]}"; do
         key=$(cut -d= -f1 <<< "$item")
+        val=$(cut -d= -f2 <<< "$item")
         if [ "$key" = "hypervisor" ]; then
-            val=$(cut -d= -f2 <<< "$item")
             hypervisor="$val"
         fi
+        if [ "$key" = "rules_dev" ]; then
+            export RULES_DEV="$val"
+        fi
 	done
 
     case "$hypervisor" in
     kvm)
-        FLOPPY_DEV=/dev/fd0
         exec {RESULT_FD}> /dev/ttyS1
         add_cleanup close_fd ${RESULT_FD}
         exec {MONITOR_FD}> /dev/ttyS2
@@ -81,7 +83,6 @@ prepare_helper() {
 		iptables -P OUTPUT DROP
 		ip6tables -P OUTPUT DROP
 		ip link set eth0 up
-        FLOPPY_DEV=/dev/xvdc
         domid=$(xenstore-read domid)
         exec {RESULT_FD}> >(xargs -l1 xenstore-write /local/domain/0/snf-image-helper/$domid)
         add_cleanup close_fd ${RESULT_FD}

snf-image-helper/snf-image-helper.in

@@ -51,24 +51,24 @@ fi
 
 prepare_helper
 
-if [ ! -b "$FLOPPY_DEV" ]; then
-    log_error "Floppy device is not present!"
+if [ ! -b "$RULES_DEV" ]; then
+    log_error "Device file hosting the rules file: \`$RULES_DEV' does not exist"
 fi
 
-floppy=$(mktemp -d --tmpdir floppy.XXXXXX)
-add_cleanup rmdir "$floppy"
+rules=$(mktemp -d --tmpdir rules.XXXXXX)
+add_cleanup rmdir "$rules"
 
-$MOUNT $FLOPPY_DEV $floppy
-add_cleanup umount "$floppy"
+$MOUNT $RULES_DEV $rules
+add_cleanup umount "$rules"
 
-if [ -f "$floppy/rules" ]; then
-    source "$floppy/rules"
+if [ -f "$rules/rules" ]; then
+    source "$rules/rules"
 else
-    log_error "Floppy does not contain \`rules\' file"
+    log_error "$RULES_DEV does not contain \`rules\' file"
 fi
 
-if [ -f "$floppy/unattend.xml" ]; then
-    export SNF_IMAGE_UNATTEND="$floppy/unattend.xml"
+if [ -f "$rules/unattend.xml" ]; then
+    export SNF_IMAGE_UNATTEND="$rules/unattend.xml"
 fi
 
 if [ -n "$SNF_IMAGE_PROPERTIES" ]; then