Fix #2225869 (Regression in attachment loading / Exchange 2003)

* The fix to bug #2191778 inadvertently broke attachment loading for
  Exchange 2003 servers; the server responds with a 403 error (indicating
  an authentication issue)
* All other communications with the server work properly
* We use a slightly different set of calls in the case of attachments (we
  wanted to change as little as possible in the fix to #2191778) than we
  do in the other cases
* The fix here is to use the same calling sequence for attachments that we
  use elsewhere
* This fix has been observed to work on multiple servers, and in various
  SSL scenarios (on/off, trusted/untrusted)

Change-Id: Ie2804ddcbfa2b10edff42f7a3811734c325e933d
1 file changed