Ada: fix initialization issue in examples

Detected by
```
gnatprove -Pclient.gpr --level=4 -j12
```

wrapper/Ada/tls_client.adb

@@ -204,8 +204,8 @@ package body Tls_Client with SPARK_Mode is
       Output : WolfSSL.Write_Result;
 
       Result : WolfSSL.Subprogram_Result;
-      DTLS   : Boolean;
-      PSK    : Boolean;
+      DTLS   : Boolean := False;
+      PSK    : Boolean := False;
    begin
       Result := WolfSSL.Initialize;
       if Result /= Success then

wrapper/Ada/tls_server.adb

@@ -162,7 +162,7 @@ package body Tls_Server with SPARK_Mode is
       Ch : Character;
 
       Result : WolfSSL.Subprogram_Result;
-      DTLS, PSK : Boolean;
+      DTLS, PSK : Boolean := True;
       Shall_Continue : Boolean := True;
 
       Input  : WolfSSL.Read_Result;