In case of read / set error of I2C device always exit OPCUA server.

This way the PLC program can handle the exception accordingly
rather that simply hide it as till now.

coupler/mod_io_i2c.h

@@ -113,6 +113,7 @@ static int setRelayState(int command, int i2c_addr)
     {
         /* ERROR HANDLING: i2c transaction failed */
         printf("Error writing to i2c slave (0x%x).\n", i2c_addr);
+        exit(1);
     }
     close(file);
     return 0;
@@ -156,11 +157,13 @@ static int getDigitalInputState(int i2c_addr, char **digital_input)
     {
         /* ERROR HANDLING: i2c transaction failed */
         printf("Error writing to i2c slave (0x%x).\n", i2c_addr);
+        exit(1);
     }
     if (read(file, read_buf, 1) != 1)
     {
         /* ERROR HANDLING: i2c transaction failed */
         printf("Error reading digital input from i2c slave (0x%x).\n", i2c_addr);
+        exit(1);
     }
     else
     {
@@ -208,11 +211,13 @@ static int getAnalogInputStateAIN(int i2c_addr, int **analog_input, uint8_t read
     {
         /* ERROR HANDLING: i2c transaction failed */
         printf("Error writing to i2c slave (0x%x).\n", i2c_addr);
+        exit(1);
     }
     if (read(file, read_buf, 2) != 2)
     {
         /* ERROR HANDLING: i2c transaction failed */
         printf("Error reading analog input from i2c slave (0x%x).\n", i2c_addr);
+        exit(1);
     }
     else
     {