[leaseinfo] write lease data to file

APIs for extracting lease information and writing to file pointer of
your choice.
Information extracted in dhcpcd-like format (ie. VAR=VAL).
Used by system updater infra on lease arrival.
Currently, variables mainly needed by netconfig are printed.
leaseinfo: address and routing related fixes
Missing /dev/rfkill is not an error, reduce loglevel
TODO: remove security audit
TODO: remove repo location and obs project location
TODO: remove infiniband from other link layers
TODO: remove sysconfig split
TODO: move dhcp4 save-state to existing section
Merge branch 'tweak_todo_list' fom github pull #11
dhcp4: don't use offered address in initial request

Do not send initial request using the offered IP address as source
address or server address in destination, but broadcast on layer 2
and 3 (RFC 2131, Section 3.1.3).
dhcp4: set fsm state before building the message

The state is required to distinguish e.g. between different request
types while building the message, not only to handle responses.
Merge pull request #12 from mtomaschewski/dhcp-request-1

dhcp4 request fixes 1
remove TODO file, moved to individual github issues
Remove newline from debug output in __ni_config_parse_ifconfig_source
Merge pull request #85 from olafhering/tweak_todo_list
Merge pull request #86 from olafhering/ni_config_parse_ifconfig_source-newline
Readded a TODO referencing github issues
dhcp6: fixed to accept low preference server offers

We wait until retransmit timeout before we accept
offers from low preference servers.
We may make it configurable how long to wait later.
Log and return error from nl_send_auto
Return -NLE_NOMEM if __ni_nl_cb_clone fails