package_rpm: Fix attemptonly and suggest packages

package_rpm: Fix attemptonly and suggest packages

[YOCTO #1325] [YOCTO #1366]

Packages that were in the PACKAGE_ATTEMPTONLY and SUGGESTS were not
being properly found, which was causing image creation failures.

In PACKAGE_ATTEMPTONLY, when an item was not found, it caused an
error.  This should have been a note, followed by skipping the
package.

The SUGGESTS processing was simply broken.  It was using a
non-existant function, due to an apparently typo.

In addition to the above, the MLPREFIX processing was not being
done properly, preventing multilib packages from working in this
with PACKAGE_ATTEMPTONLY.  (SUGGESTS doesn't need this as the names
are munged when creating the packages.)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>