torture/ntlm_auth: do not assume a line is less than 2047 bytes

torture/ntlm_auth: do not assume a line is less than 2047 bytes

These tests would fail when ran in our cloud. This was due to lines that
were more than 2047 bytes in length, causing us to fail readLine with a
ReadChildError. This fix lets it read lines of any length, but in 2047
byte segments.

Signed-off-by: Bob Campbell <bobcampbell@catalyst.net.nz>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>