Properly free the memory when RpcChannel_Send() fails.

Properly free the memory when RpcChannel_Send() fails.

At few places in the code, when RpcChannel_Send() function fails,
the result (fourth argument to the function) is not freed which might
result in a memory leak.

Addressed few references by adding 'RpcChannel_Free(...)' calls
in the necessary error code paths.

For toolbox-cmd application, added a new function ToolsCmd_FreeRPC
which internally calls RpcChannel_Free function to free the memory
allocated from ToolsCmd_SendRPC calls. Modified toolboxcmd-shrink.c
to use the new function to free the memory.