Move the lsa code across to the changed args for lookup_name, and surround it

Move the lsa code across to the changed args for lookup_name, and surround it
in become_root()/unbecome_root().

Also only allocate the memory the client reqests - and don't allow the client
to trigger an SMB_ASSERT if they ask for 'more'.

Up the maximum number of sids allowed, and note that this is an arbiary guess,
and can be raised without consequence.

Andrew Bartlett