tests: Use ofctl_strip consistently.

tests: Use ofctl_strip consistently.

The ofctl_strip shell function was introduced a little while ago.  It makes
test results easier to read, in my opinion, by removing uninteresting
bits.  This commit adopts ofctl_strip throughout the tests.

This is useful in an upcoming commit that adds additional fields that
should also be stripped to ovs-ofctl output.

Signed-off-by: Ben Pfaff <blp@nicira.com>