logging: use ISO-like timestamp in file log

Also update suricata.yaml to show this default, as updating the
"default-log-format" does not affect the file output.

src/util-debug.h

@@ -74,7 +74,7 @@ typedef enum {
 } SCLogOPType;
 
 /* The default log_format, if it is not supplied by the user */
-#define SC_LOG_DEF_FILE_FORMAT      "[%i - %m] %t %d: %S: %M"
+#define SC_LOG_DEF_FILE_FORMAT      "[%i - %m] %z %d: %S: %M"
 #define SC_LOG_DEF_LOG_FORMAT_REL   "%D: %S: %M"
 #define SC_LOG_DEF_LOG_FORMAT_RELV  "%d: %S: %M"
 #define SC_LOG_DEF_LOG_FORMAT_RELVV "[%i] %d: %S: %M"

suricata.yaml.in

@@ -577,6 +577,7 @@ logging:
       enabled: yes
       level: info
       filename: suricata.log
+      # format: "[%i - %m] %z %d: %S: %M"
       # type: json
   - syslog:
       enabled: no