[VPP-684] Adding ip address which mask length exceeding upper limit, will meet segment fault when pinging.

[vvalderrv]

Add IP address which mask length exceeding upper limit , then ping this IP from peer, we will meet a segment fault.
So we should fix it and check the mask length first.

vpp# set int ip address GigabitEthernet0/4/0 23.1.2.10/300
vpp#
vpp# show int address
GigabitEthernet0/4/0 (up):
23.1.2.10/300
GigabitEthernet0/5/0 (dn):
local0 (dn):

vpp#
Program received signal SIGSEGV, Segmentation fault.
arp_input (vm=0xae8cc0 <vlib_global_main>, node=0x7fffc5012800, frame=0x7fffc4dd6600)
at /home/wanghui/vpp_git/vpp/build-data/../vnet/vnet/ethernet/arp.c:1053
warning: Source file is more recent than executable.
1053 if (adj0->lookup_next_index != IP_LOOKUP_NEXT_ARP)
Missing separate debuginfos, use: debuginfo-install glibc-2.17-78.el7.x86_64 openssl-libs-1.0.1e-42.el7.x86_64 zlib-1.2.7-13.el7.x86_64
(gdb) bt
#0 arp_input (vm=0xae8cc0 <vlib_global_main>, node=0x7fffc5012800, frame=0x7fffc4dd6600)
at /home/wanghui/vpp_git/vpp/build-data/../vnet/vnet/ethernet/arp.c:1053
#1 0x00007ffff7547f2a in dispatch_node (vm=0xae8cc0 <vlib_global_main>, node=0x7fffc5012800, type=<optimized out>, dispatch_state=<optimized out>,
frame=<optimized out>, last_time_stamp=25677255563679) at /home/wanghui/vpp_git/vpp/build-data/../vlib/vlib/main.c:996
#2 0x00007ffff7548115 in dispatch_pending_node (vm=vm@entry=0xae8cc0 <vlib_global_main>, p=0x7fffc4e105c4, last_time_stamp=<optimized out>)
at /home/wanghui/vpp_git/vpp/build-data/../vlib/vlib/main.c:1134
#3 0x00007ffff75487be in vlib_main_loop (vm=0xae8cc0 <vlib_global_main>) at /home/wanghui/vpp_git/vpp/build-data/../vlib/vlib/main.c:1518
#4 vlib_main (vm=vm@entry=0xae8cc0 <vlib_global_main>, input=input@entry=0x7fffc5603fa0)
at /home/wanghui/vpp_git/vpp/build-data/../vlib/vlib/main.c:1653
#5 0x00007ffff77a5a83 in thread0 (arg=11439296) at /home/wanghui/vpp_git/vpp/build-data/../vlib/vlib/unix/main.c:432
#6 0x00007ffff660c450 in clib_calljmp () at /home/wanghui/vpp_git/vpp/build-data/../vppinfra/vppinfra/longjmp.S:110
#7 0x00007fffffffd320 in ?? ()
#8 0x00007ffff77a62b1 in vlib_unix_main (argc=<optimized out>, argv=<optimized out>)
at /home/wanghui/vpp_git/vpp/build-data/../vlib/vlib/unix/main.c:488
#9 0x0000000000000000 in ?? ()
(gdb)