Fix uuid-ossp regression tests based on buildfarm feedback.

The previous version of these tests expected uuid_generate_v1() to always
emit MAC addresses with the local-admin and multicast address bits zero.
However, several of the buildfarm critters are reporting values with the
local-admin bit set.  (Perhaps they're running inside VMs or jails.)
And a couple are reporting values with the multicast bit set, probably
meaning that the UUID library couldn't read the system MAC address.

Also, it emerges that if OSSP UUID can't read the system MAC address, it
falls back to V1MC behavior wherein the whole node field gets randomized
each time, breaking the test that expected the node field to remain stable
in V1 output.  (It looks like e2fs doesn't behave that way, though.)

It's not entirely clear why we can't get a system MAC address, since the
buildfarm scripts would not work without internet access.  Nonetheless,
the regression tests had better cope with the case, so adjust the tests
to expect these behaviors.