Issue #118 - Convert string to byte string on common.py

[Futabay]

This PR is to fix bugs found during RAF, RCF, and CLTU API testings (#117 #118 #128 #129 )

RAF/RCF API Test: The following strings need to be converted to byte-strings https://github.com/NASA-AMMOS/AIT-DSN/blob/4780d6d5c54a2b7b6ee71285bd08d15e2c937129/ait/dsn/sle/common.py#L435

https://github.com/NASA-AMMOS/AIT-DSN/blob/4780d6d5c54a2b7b6ee71285bd08d15e2c937129/ait/dsn/sle/common.py#L454

https://github.com/NASA-AMMOS/AIT-DSN/blob/4780d6d5c54a2b7b6ee71285bd08d15e2c937129/ait/dsn/sle/common.py#L465

CLTU API Test The following need to be converted to byte object: https://github.com/NASA-AMMOS/AIT-DSN/blob/c4d74a1b2cdeb2590fc3ce66b1dc7db2c00835c9/ait/dsn/sle/cltu.py#L512

https://github.com/NASA-AMMOS/AIT-DSN/blob/c4d74a1b2cdeb2590fc3ce66b1dc7db2c00835c9/ait/dsn/sle/cltu.py#L525

[MJJoyce]

@Futabay Should this be left open pending further testing or did this cover all the str / bytearray issues for the 2.7 -> 3.x cutover?

[Futabay]

Hi @MJJoyce Yes, I agree. I would like this to keep open until the further testing is done.

[MJJoyce]

@Futabay is this wrapped up and good for merge?

[Futabay]

Hi @MJJoyce yes, this's good to merge!

[MJJoyce]

Awesome, thanks!