local-top/cryptroot could/should use wait-for-root

I just happened here after debugging bug 1202700, and saw the sleep loop below.

                # Default delay is 180s
                if [ -z "${ROOTDELAY}" ]; then
                        slumber=180
                else
                        slumber=${ROOTDELAY}
                fi

                slumber=$(( ${slumber} * 10 ))
                while [ ! -e "$cryptsource" ]; do
                        /bin/sleep 0.1
                        slumber=$(( ${slumber} - 1 ))
                        [ ${slumber} -gt 0 ] || break
                done

this is clearly better than just a single 'sleep $ROOTDELAY'
but wait-for-root usage would seemingly be better.

This is very low priority though, as it doesn't really hurt anything as it is.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: cryptsetup 2:1.4.3-4ubuntu4
ProcVersionSignature: User Name 3.10.0-3.12-generic 3.10.1
Uname: Linux 3.10.0-3-generic x86_64
ApportVersion: 2.11-0ubuntu1
Architecture: amd64
Date: Thu Jul 18 16:12:24 2013
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: cryptsetup
UpgradeStatus: No upgrade log present (probably fresh install)
crypttab: # <target name> <source device> <key file> <options>
fstab: UUID=19f8b960-2ffd-4241-befd-fc605380cba6 / ext4 defaults,discard 0 0