Fix hang when multipart upload fails validation
Fix hang when multipart upload fails validation

This is the BigCouch version of r1134942, which landed on 1.1.x after
the 1.1.0 release.  The patch is a fixup of r1126428 and is related to
COUCHDB-1174.  The chttpd version of the original patch for COUCHDB-1174
can be found in e6b09f.

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb