[#3463] Add response4 to V4 callout arguments

[#3463] Add response4 to V4 callout arguments

/src/bin/dhcp4/dhcp4_srv.cc
    Dhcpv4Srv::processLocalizedQuery4(AllocEngine::ClientContext4Ptr& ctx,
    - Added response4 argument to lease4_offer and leases4_committed callout_handles.

/src/bin/dhcp4/tests/hooks_unittest.cc
    Updated tests

/src/hooks/dhcp/lease_cmds/lease_cmds.*
    lease4_offer() handling

/src/hooks/dhcp/lease_cmds/lease_cmds_callouts.cc
    added lease4_offer callout

/src/hooks/dhcp/lease_cmds/libloadtests/load_unload_unittests.cc
    TEST_F(LeaseCmdsCbLibLoadTest, verifyCallouts4)
    TEST_F(LeaseCmdsCbLibLoadTest, verifyCallouts6) - new tests

/src/hooks/dhcp/lease_cmds/tests/lease_cmds4_unittest.cc
    TEST_F(Lease4CmdsTest, validLease4Offer)
    TEST_F(Lease4CmdsTest, validLease4OfferMultiThreading)
    TEST_F(Lease4CmdsTest, nopLeases4Committed)
    TEST_F(Lease4CmdsTest, nopLeases4CommittedMultiThreading)
    - new tests