[connman] Re-calculate DHCP timers when waking up from suspend

Modify jolla_wakeup_timer so that it keeps track of the wakeup timers,
executes them when they expire and re-calculates wait timeout when
coming out of suspend.

This is to enable reasonable DHCP timeout performance even when using
CLOCK_MONOTONIC, as converting glib to use CLOCK_BOOTTIME proved to be
more difficult than expected.
[connman] Use wakeup timers in upper level DHCP code

Previously gdhcp client code was changed to use connman wakeup
timers instead of glib timeout sources; make the corresponding
change to upper level code, too.
Merge pull request #125 from hmallat/check-dhcp-timers-on-wakeup

[connman] Re-calculate DHCP timers when waking up from suspend
dhcpv6: Remove CONFIRM message sending when connecting a link

The CONFIRM message is not sent any more as it does not make much
sense because we do not save address expiration time so we cannot
really know how long the saved address is valid anyway.

The reply to CONFIRM message does not send expiration times back
to us so we cannot get them from server either. Because of this
we need to start using SOLICITATION anyway when a link is
connected.

Thanks to Pasi Sjöholm for reporting this.