cgsnapshot: Fix possible non-null-terminated array

cgsnapshot: Fix possible non-null-terminated array

Coverity flagged a code path where the controllers[][] structure in
parse_controllers() may not have a '\0' string as its last entry.
This would break the logic in is_ctlr_on_list().

	The function may iterate past the end of the buffer looking for
	a null terminator.

	In parse_controllers: A character buffer that has not been null
	terminated is passed to a function expecting a null terminated
	string (CWE-170)

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>