tests: Rewrite code for comparing sets of ODP actions.

tests: Rewrite code for comparing sets of ODP actions.

The compare-odp-actions.pl utility isn't fully general, even for its
intended purpose of allowing sets of ODP actions to be compared
ignoring unimportant differences in ordering of output actions and
VLAN set actions.  I decided that the proper way to do it was to have
a utility that can actually parse the actions, instead of just
doing textual transformations on them.  So, this commit replaces
compare-odp-actions.pl by "ovs-dpctl normalize-actions", which is
sufficiently general for the intended purpose.

The new ovs-dpctl functionality can be easily extended to handle
differences in fields other than VLAN, but only VLAN is needed so
far.

This will be needed in an upcoming commit that in some cases
introduces redundant "set vlan" actions into the ODP actions, which
compare-odp-actions.pl doesn't tolerate.