Use package empty handle for pkg APIs (#117)

- Package methods only need an empty handle.
  Not a regular Handle with a couple of
  sockets creation/delete.

Signed-off-by: Alessandro Boch <aboch@docker.com>

addr_linux.go

@@ -16,12 +16,7 @@ const IFA_FLAGS = 0x8
 // AddrAdd will add an IP address to a link device.
 // Equivalent to: `ip addr add $addr dev $link`
 func AddrAdd(link Link, addr *Addr) error {
-	h, err := NewHandle()
-	if err != nil {
-		return err
-	}
-	defer h.Delete()
-	return h.AddrAdd(link, addr)
+	return pkgHandle.AddrAdd(link, addr)
 }
 
 // AddrAdd will add an IP address to a link device.
@@ -34,12 +29,7 @@ func (h *Handle) AddrAdd(link Link, addr *Addr) error {
 // AddrDel will delete an IP address from a link device.
 // Equivalent to: `ip addr del $addr dev $link`
 func AddrDel(link Link, addr *Addr) error {
-	h, err := NewHandle()
-	if err != nil {
-		return err
-	}
-	defer h.Delete()
-	return h.AddrDel(link, addr)
+	return pkgHandle.AddrDel(link, addr)
 }
 
 // AddrDel will delete an IP address from a link device.
@@ -98,12 +88,7 @@ func (h *Handle) addrHandle(link Link, addr *Addr, req *nl.NetlinkRequest) error
 // Equivalent to: `ip addr show`.
 // The list can be filtered by link and ip family.
 func AddrList(link Link, family int) ([]Addr, error) {
-	h, err := NewHandle()
-	if err != nil {
-		return nil, err
-	}
-	defer h.Delete()
-	return h.AddrList(link, family)
+	return pkgHandle.AddrList(link, family)
 }
 
 // AddrList gets a list of IP addresses in the system.