Fix Coverity 1220097

Fix Coverity 1220097

*** CID 1220097:  Missing unlock  (LOCK)
/src/log-file.c: 160 in LogFileWriteJsonRecord()
154             }
155         }
156
157         /* Bail early if no file pointer to write to (in the unlikely
158          * event file rotation failed. */
159         if (aft->file_ctx->fp == NULL) {
>>>     CID 1220097:  Missing unlock  (LOCK)
>>>     Returning without unlocking "aft->file_ctx->fp_mutex".
160             return;
161         }
162
163         FILE *fp = aft->file_ctx->fp;
164         char timebuf[64];
165         AppProto alproto = FlowGetAppProtocol(p->flow);