Description of problem:
After update from keepalived 2.0.10 to 2.1.5-9 in RHEL8 attempt to use use_vmac reports:

    Cannot use VMAC/ipvlan with unicast peers - clearing use_vmac

This worked in Keepalived 2.0.10.

Keepalived VRRP cluster should support the use of use_vmac, vmac_xmit_base and unicast peering.

Needed commit:

https://github.com/acassen/keepalived/pull/1733/commits/97429b3b7e6ec2f5b9c93a5d507b152bab30f919

Version-Release number of selected component (if applicable):
keepalived 2.1.5-9.

How reproducible:

Steps to Reproduce:
1. 
Start keepalived to 
$ cat keepalived.conf
! Configuration File for keepalived

global_defs {
    vrrp_version 3
    enable_script_security
    script_user root
    nftables
}

vrrp_script check_peer_HE {
    script /usr/local/bin/check_peer_HE.sh
    interval 2
}

vrrp_instance VI_1 {
    interface core
    use_vmac
    vmac_xmit_base
    priority 100
    advert_int 1
    virtual_router_id 51
    virtual_ipaddress {
        10.0.0.1
    }
    unicast_src_ip 10.0.0.3
    unicast_peer {
      10.0.0.2
    }
    track_script {
	check_peer_HE
    }
    garp_master_delay 10
    garp_master_repeat 1
    garp_lower_prio_delay 10
    garp_lower_prio_repeat 1
    garp_master_refresh 60
    garp_master_refresh_repeat 2
}

Actual results:

    Cannot use VMAC/ipvlan with unicast peers - clearing use_vmac

Expected results:

Keepalived allows use_vmac with vmac_xmit_base set.

Additional info:

This is affecting a production environment, by disabling use_vmac capability and reducing high availability of a network system which contains devices that require long lived arp caches. These devices are unable to handle the failover of VRRP clusters with out the use_vmac feature.

Customer provided link to regression fix from upstream source: https://github.com/acassen/keepalived/pull/1733/commits/97429b3b7e6ec2f5b9c93a5d507b152bab30f919