Clean up state VRRP PID file

Change Id62bf18067d0b144c3e8825c7603cc1e51dca052 removes explicit
PID files clean up for keepalived and brings regression as
there is no 'process enable' for VRRP.

Always delete stale PID file if exists

Related-Bug: 1561046
Change-Id: I95a004a3acbe6a9160a19053a37fc0dd2b1875a5
(cherry picked from commit d3a8c9c)

Author: Arefiev Anton

neutron/agent/linux/keepalived.py

@@ -27,6 +27,7 @@
 
 from neutron._i18n import _
 from neutron.agent.linux import external_process
+from neutron.agent.linux import utils as linux_utils
 from neutron.cmd import runtime_checks as checks
 from neutron.common import utils
 
@@ -504,8 +505,12 @@ def callback(pid_file):
             # will be orphan and prevent keepalived process to be spawned.
             # A check here will let the l3-agent to kill the orphan process
             # and spawn keepalived successfully.
+            # Also removes stale pid file
             if vrrp_pm.active:
-                vrrp_pm.disable()
+                vrrp_pm.disable(delete_pid_file=False)
+
+            linux_utils.delete_if_exists(self.get_vrrp_pid_file_name(pid_file),
+                                         run_as_root=vrrp_pm.run_as_root)
 
             cmd = ['keepalived', '-P',
                    '-f', config_path,