r15796: this talloc_reference() was causing a memory leak on every NTVFS

r15796: this talloc_reference() was causing a memory leak on every NTVFS
request. The problem is that the talloc_free() in
smbsrv_send_reply_nosign() frees this reference, but doesn't free the
memory iself, thus leaving it attached to the connection context.

Metze, what was the idea behind this reference? If we need it, then we
need a corresponding talloc_free() to go with it.