fib_trie: Fix uninitialized variable warning

fib_trie: Fix uninitialized variable warning

The 0-day kernel test infrastructure reported a use of uninitialized
variable warning for local_table due to the fact that the local and main
allocations had been swapped from the original setup.  This change corrects
that by making it so that we free the main table if the local table
allocation fails.

Fixes: 3ee5fffe8 ("ipv4: FIB Local/MAIN table collapse")
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>