David Jaša authored Dec 19, 2022 and Filip Pokryvka committed Jan 12, 2023

MPTCP support: steps and cleanup

MPTCP in NM depends on respective sysctl settings. Therefore
infrastructure is added that allows to save all sysctls matching a given
pattern, pattern specified as:

    nmci.cleanup.cleanup_add_sysctls(PATTERN)

is passed verbatim to:

    sysctl -a --pattern PATTERN

Sysctl infrastructure may also be used to tweak some sysctl in a step
and having it automatically reverted during cleanup:

    * Set sysctl "my.key" to value "My value"

Sysctl clean-up is on purpose implemented in a naïve way when repeated
setting of the same sysctl will create respective number of cleanup
actions of which only last one is required. The unique_tag looks to do exact
opposite of what we need here and neat solution is out-of-scope of this
MR.