Make troubleshoot work with dracut ramdisks

Currently, calling the troubleshoot function in a ramdisk script
doesn't work as expected on dracut ramdisks.  This adds an alternate
troubleshoot implementation that will behave as intended.

I did not make it conditional on a kernel param as was done in the
original because dracut can behave strangely if you allow it to
continue after an error.  Always dropping to a shell immediately
should be less confusing.

Change-Id: I98000f4ac6d7890b1f44fe4d10394ac0ea332fcb

elements/dracut-ramdisk/extra-data.d/scripts/module/deploy-cmdline.sh

@@ -11,8 +11,6 @@ rootok=1
 # Dracut doesn't correctly parse the ip argument passed to us.
 # Override /proc/cmdline to rewrite it in a way dracut can grok.
 sed 's/\(ip=\S\+\)/\1:::off/' /proc/cmdline > /run/cmdline
-# Map the existing "troubleshoot" kernel param to the Dracut equivalent.
-sed -i 's/troubleshoot=/rd.shell=/' /run/cmdline
 mount -n --bind -o ro /run/cmdline /proc/cmdline
 # Force Dracut to re-read the cmdline args
 CMDLINE=

elements/dracut-ramdisk/init.d/00-override-troubleshoot

@@ -0,0 +1,7 @@
+# NOTE(bnemec): Dracut provides its own emergency shell, and it doesn't
+# seem to allow directly starting bash as the existing troubleshoot function
+# does.
+function troubleshoot() {
+    echo "Starting troubleshooting shell."
+    emergency_shell
+}