s2n_alpn_rcv: skip *or* read, not skip *and* read.
s2n_alpn_rcv: skip *or* read, not skip *and* read.

When iterating over the client protos list, if the length of the
current client proto doesn't match the one we're searching for, the
proto is skipped over, but this is followed by an unconditional read,
leading to various errors depending on the set of ALPN from the
client. [chrome 43 is sending 4 items].

PKRoma/s2n,colmmacc/s2n,PKRoma/s2n,PKRoma/s2n,wcs1only/s2n,colmmacc/s2n,gibson-compsci/s2n,awslabs/s2n,jldodds/s2n,raycoll/s2n,wcs1only/s2n,wcs1only/s2n,awslabs/s2n,wcs1only/s2n,colmmacc/s2n,raycoll/s2n,jldodds/s2n,wcs1only/s2n,bpdavidson/s2n,jldodds/s2n,bpdavidson/s2n,PKRoma/s2n,PKRoma/s2n,raycoll/s2n,bpdavidson/s2n,gibson-compsci/s2n,gibson-compsci/s2n,gibson-compsci/s2n,PKRoma/s2n,jldodds/s2n,bpdavidson/s2n,awslabs/s2n,bpdavidson/s2n,bpdavidson/s2n,raycoll/s2n,alexeblee/s2n,gibson-compsci/s2n,colmmacc/s2n,PKRoma/s2n,alexeblee/s2n,awslabs/s2n,alexeblee/s2n,colmmacc/s2n,alexeblee/s2n,awslabs/s2n,wcs1only/s2n,awslabs/s2n,PKRoma/s2n,jldodds/s2n,alexeblee/s2n,alexeblee/s2n,wcs1only/s2n,raycoll/s2n,gibson-compsci/s2n,wcs1only/s2n,raycoll/s2n,colmmacc/s2n