test_ipaddr.cc: memset with 0 and not '0'

test_ipaddr.cc: memset with 0 and not '0'

Fix for:

CID 1405070 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405071 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405073 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405074 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405075 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405077 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405083 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405086 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
CID 1405087 (#1 of 1): Memset fill value of '0' (NO_EFFECT)
 bad_memset: "memset" with fill value "'0'" (the zero character).
 memset(&net, 48, 28UL). (CWE-665)

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>