Fixed payload size issue

[Akshata440]

What does this Pull Request accomplish?

Changes made to fix the issue #658

releases\1.5 branch will be fast-forwarded to include this fix and minor/patch release will be published with this bug fix as it fixes showstopper bug for ENET frames in XNET.

Why should this Pull Request be merged?

While calling WriteFrame API, we need to pass in buffer with last 4 bytes of buffer reserved for adding FCS (frame checksum). in gRPC service we take payload data as input from user and allocate buffer and copy payload that user has sent in. Earlier we had missed allocating extra 4 bytes for the FCS while allocating buffer for copying data. Hence, 4 bytes of the payload were not being written correctly. I have added a new constant called ETHERNET_FRAME_FCS_SIZE which is now used for calculating payload sizes while reading and writing frames.

What testing has been done?

Ran system tests in #654 to confirm the whole payload is read correctly.
Before :

After :

[mgumble]

Well this is a major bummer, releasing XNET with this bug. @asumit do you think we just didn't do enough manual testing to catch this before creating the release?

@Akshata440 You mentioned we would fast forward the release branch, but we need to update the artifacts too and create yet another release I guess with a minor version bump?
@astarche Thoughts on versioning?

[astarche]

The version should be 1.5.1. The idea of fast-forwarding and using the same branch sounds right to me as well.

[doshirohan]

Well this is a major bummer, releasing XNET with this bug. @asumit do you think we just didn't do enough manual testing to catch this before creating the release?
@Akshata440 You mentioned we would fast forward the release branch, but we need to update the artifacts too and create yet another release I guess with a minor version bump?

We did test the API manually and we were in process of automating that via test when we encountered the issue. During testing, we had used XNET C API for generating frames and were reading those gRPC API in loopback test to validate the data. This had passed, though this issue had turned out to be in write frame itself which we couldn't catch with that manual test.

We are planning to create 1.5.1 patch release for this once the PR goes in.

@Akshata440 @mgumble @astarche @reckenro @asumit