ofp-util: Abstract table miss configuration and fix related bugs.

The ofproto implementation has had an abstraction layer on top of
OFPTC11_TABLE_MISS for a while.  This commit pushes that abstraction layer
farther down, into ofp-util.  This will be more useful in an upcoming
commit.

During the conversion I realized that the previous implementation was
not entirely correct.  In particular, the OpenFlow 1.3+ "table mod" was
still being treated as if it had table miss configuration bits, even
though it doesn't.  This commit fixes that issue and updates the tests.

OpenFlow 1.4 adds some more OFPTC_* flags that this new abstraction doesn't
yet support, but OVS didn't support those flags any better before this
commit, so abstracting those is left as future work.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>