r16241: Fix Klocwork #106 and others like it.

r16241: Fix Klocwork #106 and others like it.
Make 2 important changes. pdb_get_methods()
returning NULL is a *fatal* error. Don't try
and cope with it just call smb_panic. This
removes a *lot* of pointless "if (!pdb)" handling
code. Secondly, ensure that if samu_init()
fails we *always* back out of a function. That
way we are never in a situation where the pdb_XXX()
functions need to start with a "if (sampass)"
test - this was just bad design, not defensive
programming.
Jeremy.