Unix: preserve automatic backup-header errors

Limit backup retry recovery to credential errors. Restore header selection
and rethrow other failures, including cancellation, in CLI and GUI.

Add regression coverage for fallback and credential recovery.

src/Main/GraphicUserInterface.cpp

@@ -1091,12 +1091,18 @@ namespace VeraCrypt
 						{
 							volume = mountWithProtectionRecovery();
 						}
-						catch (...)
+						catch (PasswordException&)
 						{
 							options.UseBackupHeaders = false;
 							autoBackupHeaderUsed = false;
 							ShowWarning (e);
 						}
+						catch (...)
+						{
+							options.UseBackupHeaders = false;
+							autoBackupHeaderUsed = false;
+							throw;
+						}
 					}
 					else
 						ShowWarning (e);

src/Main/TextUserInterface.cpp

@@ -1611,7 +1611,7 @@ namespace VeraCrypt
 					{
 						volume = mountWithProtectionRecovery();
 					}
-					catch (...)
+					catch (PasswordException&)
 					{
 						retryWithCachedPasswords = false;
 						autoBackupHeaderUsed = false;
@@ -1620,6 +1620,12 @@ namespace VeraCrypt
 						options.Password.reset();
 						options.Pim = -1;
 					}
+					catch (...)
+					{
+						autoBackupHeaderUsed = false;
+						options.UseBackupHeaders = false;
+						throw;
+					}
 				}
 				else
 				{