MFC r298448,r298464:

r298448:

Don't leak string in parse_define(..) when a macro has been found
and the parser token != TOK_ASSIGN

CID: 1007187, 1007188
Obtained from: Isilon OneFS (part of r445479)

r298464:

Use sizeof(*uuser) instead of sizeof(struct usm_user) for consistency with
the rest of the users in the file

No functional change