Revert "Don't CHECK imapserver after each APPEND"

This reverts commit 47390e03d6.

It is one of two potential candidates for the APPENDUID
regression that John Wiegley reported. We need to examine this
carefully before reintroducing this patch.

Resolved Changelog.draft.rst conflict.

Changelog.draft.rst

@@ -30,6 +30,8 @@ Changes
   we would not propagate local folders to the remote repository.
   (now tested in test03)
 
+* Revert "* Slight performance enhancement uploading mails to an IMAP
+  server in the common case." It might have led to instabilities.
 
 Bug Fixes
 ---------

offlineimap/folder/IMAP.py

@@ -568,6 +568,10 @@ class IMAPFolder(BaseFolder):
                         "failed (error). Server reponded: %s\nMessage content was: "
                         "%s" % (self, self.getrepository(), str(e), dbg_output),
                                            OfflineImapError.ERROR.MESSAGE)
+            # Checkpoint. Let it write out stuff, etc. Eg searches for
+            # just uploaded messages won't work if we don't do this.
+            typ, dat = imapobj.check()
+            assert(typ == 'OK')
 
             # get the new UID, default to 0 (=unknown)
             uid = 0
@@ -587,11 +591,6 @@ class IMAPFolder(BaseFolder):
                             "'%s'" % str(resp))
             else:
                 # Don't support UIDPLUS
-                # Checkpoint. Let it write out stuff, etc. Eg searches for
-                # just uploaded messages won't work if we don't do this.
-                typ, dat = imapobj.check()
-                assert(typ == 'OK')
-
                 uid = self.savemessage_searchforheader(imapobj, headername,
                                                        headervalue)
                 # If everything failed up to here, search the message