addrconf: added optional lease handling flag bitmap
addrconf: propagate handling flags
compat: adjusted redhat backend to compile again
ifup: no timeout on optional leases (bnc#875154)
ifstatus: no failure if peer lease is up (bnc#875154)
Merge pull request #227 from mtomaschewski/dhcp4or6

client: no failures/timeouts if optional peer lease is up (bnc#875154)