Merge branch 'mptcp-improve-set-flags-command-and-update-self-tests'

Mat Martineau says:

====================
mptcp: Improve set-flags command and update self tests

Patches 1-3 allow more flexibility in the combinations of features and
flags allowed with the MPTCP_PM_CMD_SET_FLAGS netlink command, and add
self test case coverage for the new functionality.

Patches 4-6 and 9 refactor the mptcp_join.sh self tests to allow them to
configure all of the test cases using either the pm_nl_ctl utility (part
of the mptcp self tests) or the 'ip mptcp' command (from iproute2). The
default remains to use pm_nl_ctl.

Patches 7 and 8 update the pm_netlink.sh self tests to cover the use of
endpoint ids to set endpoint flags (instead of just addresses).
====================

Link: https://lore.kernel.org/r/20220205000337.187292-1-mathew.j.martineau@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>