Fix keepalived path in systemd drop-in

[venkyt-arista]

Commit d548304 changed keepalived path from /usr/sbin to /usr/bin, but the systemd drop-in still referenced the /usr/sbin path.

How to use

Add the keepalived sysext, enable the service (systemctl enable --now keepalived), and verify that the systemd service comes up fine:

Nov 06 14:53:15 foo.example.com Keepalived[23170]: Warning - keepalived has no configuration to run
Nov 06 14:53:15 foo.example.com systemd[1]: Started keepalived.service - LVS and VRRP High Availability Monitor.

Testing done

Tested by adding the keepalived sysext, and verified that the service comes up fine.

Without this change, on enabling keepalived, this is the status:

$ systemctl status keepalived
× keepalived.service - LVS and VRRP High Availability Monitor
     Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; preset: disabled)
    Drop-In: /usr/lib/systemd/system/keepalived.service.d
             └─10-keepalived.conf
     Active: failed (Result: exit-code) since Thu 2025-11-06 14:38:29 UTC; 3s ago
   Duration: 1h 43min 27.313s
    Process: 20747 ExecStartPre=/bin/bash -c set -e; mkdir -p /etc/keepalived/; if ! [ -e /etc/keepalived/keepalived.conf ]; then touch /etc/keepalived/keepalived.conf; fi (code=exited, status=0/SUCCESS)
    Process: 20750 ExecStart=/usr/sbin/keepalived --use-file /etc/keepalived/keepalived.conf $KEEPALIVED_OPTIONS (code=exited, status=203/EXEC)
        CPU: 12ms

Nov 06 14:38:29 foo.example.com systemd[1]: keepalived.service: Start request repeated too quickly.
Nov 06 14:38:29 foo.example.com systemd[1]: keepalived.service: Failed with result 'exit-code'.
Nov 06 14:38:29 foo.example.com systemd[1]: Failed to start keepalived.service - LVS and VRRP High Availability Monitor.

Services comes up fine with the fix.