ip address: do not set mngtmpaddr option for IPv4 addresses

ip address: do not set mngtmpaddr option for IPv4 addresses

'mngtmpaddr' option make the kernel manage temporary addresses
created from the specified one as template on behalf of Privacy
Extensions (RFC3041). This option should be available only for
IPv6 addresses, as correctly stated in the manpage.

However it is possible to set mngtmpaddr on IPv4 addresses, too:

$ ip link add dummy0 type dummy
$ ip -4 addr add 192.168.1.1 dev dummy0 mngtmpaddr
$ ip a
1: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN group default qlen 1000
   link/ether 1a:6d:c6:96:ca:f8 brd ff:ff:ff:ff:ff:ff
   inet 192.168.1.1/32 scope global mngtmpaddr dummy0
      valid_lft forever preferred_lft forever

Fix this adding a check on the protocol family before setting
IFA_F_MANAGETEMPADDR flag.

Fixes: 5b7e21c417bea ("add support for IFA_F_MANAGETEMPADDR")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>