create-diff-object: fixup new function handling

Lets try again.  This time with a check to see if the underlying section is already included before proceeding.

The original logic in the inclusion tree code worked under the
assumption that it was the only code path marking symbols for inclusion.
Therefore, if the symbol had been marked as included, it could be safely
assumed that we also already called kpatch_include_symbol() on it.  With
the special section handling marking symbols as included, however, this
assumption is not valid.

We should call kpatch_include_symbol() regardless of whether or not the
symbol has already been marked as included or not in order to possible
include the symbol's entire bundle.

Signed-off-by: Seth Jennings <sjenning@redhat.com>