Merge "Avoid race condition for reserved DHCP ports"

diff --cc neutron/agent/linux/dhcp.py
Simple merge

diff --cc neutron/api/rpc/handlers/dhcp_rpc.py
Simple merge

diff --cc neutron/common/exceptions.py
index 69acf4e36616062aa82a2c915bba8284b0960cdf,cb882975354c2b5c74a06c6fd0808d7893281d09..54800e246195e9bafe3aaa0e1072883e5d1966ef
--- 1/neutron/common/exceptions.py
--- 2/neutron/common/exceptions.py
+++ b/neutron/common/exceptions.py
@@@ -179,9 -169,13 +179,13 @@@ class PortInUse(InUse)
  
  class ServicePortInUse(InUse):
      message = _("Port %(port_id)s cannot be deleted directly via the "
 -                "port API: %(reason)s")
 +                "port API: %(reason)s.")
  
  
+ class DhcpPortInUse(InUse):
+     message = _("Port %(port_id)s is already acquired by another DHCP agent")
+ 
+ 
  class PortBound(InUse):
      message = _("Unable to complete operation on port %(port_id)s, "
                  "port is already bound, port type: %(vif_type)s, "