ClatIngress6Value.java - replace U32 ifindex with S32

These are allocated in order by the kernel, if we go
over 2 billion, we've got other problems... besides
U32 to S32 conversion will work just fine anyway.

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Iab2d4a13bf7ba45bbe8627adfdfb830f3219bc7b
1 file changed