The convertProtocols() function now throws a range error when the byte
length of a protocol is too long to fit in a Buffer.

Also added a test case in test/parallel/test-tls-basic-validations.js
to cover this.

Changed the byte length error message for protocol to correctly state
that the length must be <= 255 not < 255

Amended the test case in test/parallel/test-tls-basic-validations.js

Also changed corresponding usage in lib/tls.js

Amended the test case in test/parallel/test-tls-basic-validations.js