logging: check for fmts not being NULL

this fix is just a review of possible SIGSEGV issues in line 714
as per crash report at the bug:

```
08:35:25 Program terminated with signal 11, Segmentation fault.
08:35:25 #0  0x00007f4ebb491c5c in gf_time_fmt (dst=0x7f4eb1ff9a90 "", sz_dst=256, utime=1531470915, fmt=0)
at /home/jenkins/root/workspace/centos7-regression/libglusterfs/src/common-utils.h:714
```

fixes: bz#1600878
Change-Id: I160c391f8ac1a3456e59103d293b24e0e3fae718
Signed-off-by: Amar Tumballi <amarts@redhat.com>

2 files changed, 10 insertions, 7 deletions

diff --git a/libglusterfs/src/common-utils.c b/libglusterfs/src/common-utils.c
index 09f0caa7e8a..d7888f526df 100644
--- a/libglusterfs/src/common-utils.c
+++ b/libglusterfs/src/common-utils.c
@@ -3097,9 +3097,8 @@ static const char *__gf_zerotimes[] = {
 };
 
 void
-_gf_timestuff (gf_timefmts *fmt, const char ***fmts, const char ***zeros)
+_gf_timestuff (const char ***fmts, const char ***zeros)
 {
-        *fmt = gf_timefmt_last;
         *fmts = __gf_timefmts;
         *zeros = __gf_zerotimes;
 }
diff --git a/libglusterfs/src/common-utils.h b/libglusterfs/src/common-utils.h
index 569147e3718..fc581de4998 100644
--- a/libglusterfs/src/common-utils.h
+++ b/libglusterfs/src/common-utils.h
@@ -698,19 +698,23 @@ typedef enum {
 static inline char *
 gf_time_fmt (char *dst, size_t sz_dst, time_t utime, unsigned int fmt)
 {
-        extern void _gf_timestuff (gf_timefmts *, const char ***, const char ***);
+        extern void _gf_timestuff (const char ***, const char ***);
         static gf_timefmts timefmt_last = (gf_timefmts) - 1;
         static const char **fmts;
         static const char **zeros;
         struct tm tm, *res;
         int localtime = 0;
 
-        if (timefmt_last == (gf_timefmts) - 1)
-                _gf_timestuff (&timefmt_last, &fmts, &zeros);
-        if (timefmt_last < fmt) fmt = gf_timefmt_default;
+        if (timefmt_last == ((gf_timefmts)-1)) {
+                _gf_timestuff (&fmts, &zeros);
+                timefmt_last = gf_timefmt_last;
+        }
+        if (timefmt_last <= fmt) {
+                fmt = gf_timefmt_default;
+        }
         localtime = gf_log_get_localtime ();
         res = localtime ? localtime_r (&utime, &tm) : gmtime_r (&utime, &tm);
-        if (utime && res != NULL) {
+        if (utime && (res != NULL)) {
                 strftime (dst, sz_dst, fmts[fmt], &tm);
         } else {
                 strncpy (dst, "N/A", sz_dst);