r20090: Fix a class of bugs found by James Peach. Ensure

r20090: Fix a class of bugs found by James Peach. Ensure
we never mix malloc and talloc'ed contexts in the
add_XX_to_array() and add_XX_to_array_unique()
calls. Ensure that these calls always return
False on out of memory, True otherwise and always
check them. Ensure that the relevent parts of
the conn struct and the nt_user_tokens are
TALLOC_DESTROYED not SAFE_FREE'd.
James - this should fix your crash bug in both
branches.
Jeremy.