Change drive_prep() to look for the device instead of the mount

There is a subtle but annoying bug where using tab completion to give
the mount path adds a "/" at the end. When `grep` is run to check
if the image is mounted it searches with the trailing slash.

By looking for the partition instead we can avoid this small usability
issue which can cause confusion.
modifying kernel command line to restore RHEL 6./x behavior for xen
block device mapping per
https://bugzilla.redhat.com/show_bug.cgi?id=729586
(wish I had known this months ago kudos to mostlygeek)
Strip trailing / from $IMGLOC

This reverts the previous change of checking for the mount point instead
of if $IMGLOC exists.

This change strips the trailing slash from $IMGLOC so the user does not
need to remember to remove the trailing slash manually.
Merge pull request #2 from mostlygeek/improve-usability

Change drive_prep() to look for the device instead of the mount
modified to catch up to ebs_volume script. changed boot params, merge
request etc
Merge branch 'master' of github.com:ckolos/aws-scripts

merge request
need -F to force mke2fs to create fs on raw device
renamed scripts to be more indicative of function
non-partitioned images seem to be the only ones that work "properly"
with m1.small images, so noted that in docs
fixed typo in docs