Added !SSPI to the features list of the HTTP digest tests, as SSPI
based builds now use the Windows SSPI messaging API rather than the
internal functions, and we can't control the random numbers that get
used as part of the digest.
a fresh connection to be made in such cases and the request retransmitted.
This should fix test case 160. Added test case 1079 in an attempt to
test a similar connection dropping scenario, but as a race condition, it's
hard to test reliably.