image.bbclass: The wrong name is being used for the debug filesystem

image.bbclass: The wrong name is being used for the debug filesystem

[YOCTO #9487]

The debug filesystem file name is ending in "debug_tar", it should be simply
"tar".  Strip the "debug_" piece as necessary.

To avoid deleting the tar ball, when we've asked for just the tarball we need
to check 't' and not 'realt'.

The two hunks were suggested by RP.  I've implemented and verify they work
with the settings:

PACKAGE_CLASSES = "package_rpm"
IMAGE_GEN_DEBUGFS = '1'

IMAGE_FSTYPES_DEBUGFS = "tar.bz2"

IMAGE_FSTYPES_DEBUGFS = "tar.gz"

and

IMAGE_FSTYPES_DEBUGFS = "tar"

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>