integration-test: Update TCP keep alive interval config

With latest FreeRTOS TCP/IP stack, due to a timing issue, most of the
MQTT tests fail on FVP, because of TCP keep alive timeout. Therefore,
increase the TCP keep alive timeout `ipconfigTCP_KEEP_ALIVE_INTERVAL`
from `20` to `300` seconds.

Signed-off-by: Devaraj Ranganna <[email protected]>

Author: urutva

applications/freertos_iot_libraries_tests/configs/freertos_config/FreeRTOSIPConfig.h

@@ -301,7 +301,7 @@ extern void vLoggingPrintf( const char * pcFormatString,
 
 /* Include support for TCP keep-alive messages. */
 #define ipconfigTCP_KEEP_ALIVE              ( 1 )
-#define ipconfigTCP_KEEP_ALIVE_INTERVAL     ( 20 ) /* in seconds */
+#define ipconfigTCP_KEEP_ALIVE_INTERVAL     ( 300 ) /* in seconds */
 
 /* Include all API's and code that is needed for the IPv4 protocol.
  * When defined as zero, the application should uses IPv6. */