Added control_client request acknowledgement and changed it's packet sending method to sendmsg

[bskdany]

Changes

• pad_client now sends the packet all at once with sendmsg instead of send
• pad_server receives the request and answers with an acknowledgement
• if the pad_server doesn't send the acknowledgement by #define RCVTIMEO_SEC 3; seconds (need feedback on this) the pad_client marks the request as failed

The code was properly tested, it integrates the hybric-comm specs and works as expected

What is missing

• There is no acknowledgement with error code for incorrect or malformed headers, need comment on this part

I'm not sure if I have a different .clang-formatter somewhere or someone else is not using the one provided by the repo but I keep having formatting diffs in my commits.

[bskdany]

Created function to flush RECV_BUFFER_SIZE bytes from recv on the pad_server in the following 4 cases:

• invalid header type
• invalid header subtype
• received acknowledgement from sender
• error reading message header

[linguini1]

• received acknowledgement from sender

If we receive acknowledgement from sender, that is bad, but I would prefer that we just read the correct number of bytes from the receive buffer into nowhere (don't use the received bytes). This way we can avoid flushing the entire buffer when we know the payload size of the garbage data we want to clear.