src/common.c: fix a stack-buffer-overflow issue

ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fff4c61e7e0 at pc 0x14f2cb7ae0b9 bp 0x7fff4c61e650 sp 0x7fff4c61ddd8
WRITE of size 17 at 0x7fff4c61e7e0 thread T0
    #0 0x14f2cb7ae0b8  (/lib64/libasan.so.5+0xb40b8)
    ofiwg#1 0x14f2cb7aedd2 in vsscanf (/lib64/libasan.so.5+0xb4dd2)
    ofiwg#2 0x14f2cb7aeede in __interceptor_sscanf (/lib64/libasan.so.5+0xb4ede)
    ofiwg#3 0x14f2cb230766 in ofi_addr_format src/common.c:401
    ofiwg#4 0x14f2cb233238 in ofi_str_toaddr src/common.c:780
    ofiwg#5 0x14f2cb314332 in vrb_handle_ib_ud_addr prov/verbs/src/verbs_info.c:1670
    ofiwg#6 0x14f2cb314332 in vrb_get_match_infos prov/verbs/src/verbs_info.c:1787
    ofiwg#7 0x14f2cb314332 in vrb_getinfo prov/verbs/src/verbs_info.c:1841
    ofiwg#8 0x14f2cb21fc28 in fi_getinfo_ src/fabric.c:1010
    ofiwg#9 0x14f2cb25fcc0 in ofi_get_core_info prov/util/src/util_attr.c:298
    ofiwg#10 0x14f2cb269b20 in ofix_getinfo prov/util/src/util_attr.c:321
    ofiwg#11 0x14f2cb3e29fd in rxd_getinfo prov/rxd/src/rxd_init.c:122
    ofiwg#12 0x14f2cb21fc28 in fi_getinfo_ src/fabric.c:1010
    ofiwg#13 0x407150 in ft_getinfo common/shared.c:794
    ofiwg#14 0x414917 in ft_init_fabric common/shared.c:1042
    ofiwg#15 0x402f40 in run functional/bw.c:155
    ofiwg#16 0x402f40 in main functional/bw.c:252
    ofiwg#17 0x14f2ca1b28e2 in __libc_start_main (/lib64/libc.so.6+0x238e2)
    ofiwg#18 0x401d1d in _start (/root/libfabric/fabtests/functional/fi_bw+0x401d1d)

Address 0x7fff4c61e7e0 is located in stack of thread T0 at offset 48 in frame
    #0 0x14f2cb2306f3 in ofi_addr_format src/common.c:397

  This frame has 1 object(s):
    [32, 48) 'fmt' <== Memory access at offset 48 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow (/lib64/libasan.so.5+0xb40b8)
Shadow bytes around the buggy address:
  0x1000698bbca0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000698bbcb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000698bbcc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000698bbcd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000698bbce0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x1000698bbcf0: 00 00 00 00 00 00 f1 f1 f1 f1 00 00[f2]f2 f3 f3
  0x1000698bbd00: f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1
  0x1000698bbd10: f1 f1 00 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 f2 f2
  0x1000698bbd20: f2 f2 00 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 f2 f2
  0x1000698bbd30: f2 f2 00 00 00 00 00 06 f2 f2 f2 f2 f2 f2 00 00
  0x1000698bbd40: 00 00 00 06 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb

Fixes: 5d31276 ("common: Redo address string conversions")
Signed-off-by: Honggang Li <honli@redhat.com>

src/common.c

@@ -395,14 +395,14 @@ const char *ofi_straddr(char *buf, size_t *len,
 
 uint32_t ofi_addr_format(const char *str)
 {
-	char fmt[16];
+	char fmt[17];
 	int ret;
 
+	memset(fmt, 0, sizeof(fmt));
 	ret = sscanf(str, "%16[^:]://", fmt);
 	if (ret != 1)
 		return FI_FORMAT_UNSPEC;
 
-	fmt[sizeof(fmt) - 1] = '\0';
 	if (!strcasecmp(fmt, "fi_sockaddr_in"))
 		return FI_SOCKADDR_IN;
 	else if (!strcasecmp(fmt, "fi_sockaddr_in6"))