Move unsafe call out of signal handler

Cleanup clang-tidy bugprone-signal-handler findings.
- wolfsshd: drop fprintf from interruptCatch; the main accept
  loop logs "Closing down wolfSSHD" after seeing quit set.
- sftpclient: annotate wolfSSH_SFTP_Interrupt call in
  sig_handler with NOLINT, since the function is only a single
  byte store and is safe to call from a signal handler.

apps/wolfsshd/wolfsshd.c

@@ -203,8 +203,6 @@ static void ShowUsage(void)
 static void interruptCatch(int in)
 {
     (void)in;
-    if (logFile)
-        fprintf(logFile, "Closing down wolfSSHD\n");
     quit = 1;
 }
 
@@ -2762,6 +2760,9 @@ static int StartSSHD(int argc, char** argv)
             }
 #endif
         }
+        if (quit && logFile) {
+            fprintf(logFile, "Closing down wolfSSHD\n");
+        }
     }
 
 #ifdef _WIN32

examples/sftpclient/sftpclient.c

@@ -268,7 +268,7 @@ static void sig_handler(const int sig)
     (void)sig;
 
     interrupt = 1;
-    wolfSSH_SFTP_Interrupt(ssh);
+    wolfSSH_SFTP_Interrupt(ssh); /* NOLINT(bugprone-signal-handler) */
 }
 #endif /* WS_NO_SIGNAL */