Fix issues with TCP_CONGESTION handling after r294540:
o Return back the buf[TCP_CA_NAME_MAX] for TCP_CONGESTION,

for TCP_CCALGOOPT use dynamically allocated *pbuf.

o For SOPT_SET TCP_CONGESTION do NULL terminating of string

taking from userland.

o For SOPT_SET TCP_CONGESTION do the search for the algorithm

keeping the inpcb lock.

o For SOPT_GET TCP_CONGESTION first strlcpy() the name

holding the inpcb lock into temporary buffer, then copyout.

Together with: lstewart