don't change delete_server_after, let core handle it

src/main/java/com/b44t/messenger/DcContext.java

@@ -254,21 +254,6 @@ public class DcContext {
       setConfigInt("is_muted", muted? 1 : 0);
     }
 
-    // Called for new profiles on chatmail servers that are "single device" initially;
-    // to save server disk space, we make use of that delete all messages immediately after download.
-    public void assumeSingleDevice() {
-      if (isChatmail()) {
-        setConfigInt("delete_server_after", 1 /*at once*/);
-      }
-    }
-
-    // Called when we get a hint that another device may be set up.
-    public void assumeMultiDevice() {
-      if (isChatmail() && getConfigInt("delete_server_after") == 1 /*at once*/) {
-        setConfigInt("delete_server_after", 0 /*never/automatic*/);
-      }
-    }
-
     public boolean isGmailOauth2Addr(String addr) {
       final String oauth2url = getOauth2Url(addr, "chat.delta:/foo");
       return isGmailOauth2Url(oauth2url);

src/main/java/org/thoughtcrime/securesms/InstantOnboardingActivity.java

@@ -391,7 +391,6 @@ public class InstantOnboardingActivity extends BaseActionBarActivity implements
         progressUpdate((int)progress);
       } else if (progress==1000/*done*/) {
         DcHelper.getAccounts(this).startIo();
-        dcContext.assumeSingleDevice();
         progressSuccess();
       }
     }

src/main/java/org/thoughtcrime/securesms/WelcomeActivity.java

@@ -327,7 +327,6 @@ public class WelcomeActivity extends BaseActionBarActivity implements DcEventCen
             else if (progress==1000/*done*/) {
                 DcHelper.getAccounts(this).startIo();
                 progressSuccess();
-                dcContext.assumeMultiDevice();
                 notificationController.close();
                 cleanupTempBackupFile();
             }

src/main/java/org/thoughtcrime/securesms/preferences/ListSummaryPreferenceFragment.java

@@ -138,7 +138,6 @@ public abstract class ListSummaryPreferenceFragment extends CorrectedPreferenceF
   protected void startImexInner(int accountId, int what, String imexPath, String pathAsDisplayedToUser)
   {
     DcContext dcContext = DcHelper.getAccounts(getActivity()).getAccount(accountId);
-    dcContext.assumeMultiDevice();
     this.pathAsDisplayedToUser = pathAsDisplayedToUser;
     progressWhat = what;
     dcContext.imex(progressWhat, imexPath);

src/main/java/org/thoughtcrime/securesms/qr/BackupProviderFragment.java

@@ -64,7 +64,6 @@ public class BackupProviderFragment extends Fragment implements DcEventCenter.Dc
         progressBar.setIndeterminate(true);
 
         dcContext = DcHelper.getContext(getActivity());
-        dcContext.assumeMultiDevice();
         DcHelper.getEventCenter(getActivity()).addObserver(DcContext.DC_EVENT_IMEX_PROGRESS, this);
 
         prepareThread = new Thread(() -> {

src/main/java/org/thoughtcrime/securesms/qr/BackupReceiverFragment.java

@@ -89,7 +89,6 @@ public class BackupReceiverFragment extends Fragment implements DcEventCenter.Dc
             } else if (permille == 1000) {
                 getTransferActivity().setTransferState(BackupTransferActivity.TransferState.TRANSFER_SUCCESS);
                 getTransferActivity().doFinish();
-                dcContext.assumeMultiDevice();
                 return;
             }