BackupAccountControl: silence exceptions during CreateAccount

We expect that the raidfile or HTTP file doesn't exist during CreateAccount, so
the exception message is unhelpful, so suppress it.

lib/backupstore/BackupAccountControl.cpp

@@ -15,6 +15,7 @@
 
 #include "autogen_BackupStoreException.h"
 #include "autogen_CommonException.h"
+#include "autogen_RaidFileException.h"
 #include "BackupAccountControl.h"
 #include "BackupStoreAccounts.h"
 #include "BackupStoreCheck.h"
@@ -495,6 +496,18 @@ int BackupStoreAccountControl::CreateAccount(int32_t DiscNumber, int32_t SoftLim
 
 	// Create the BackupStoreInfo and BackupStoreRefCountDatabase files:
 	mapFileSystem.reset(new RaidBackupFileSystem(mAccountID, mRootDir, mDiscSetNum));
+
+	{
+		// Taking the lock will try to GetAccountIdentifier() (for the log message) which
+		// will throw a RaidFileException(RaidFileDoesntExist) because the BackupStoreInfo
+		// file does not exist yet. We expect that! So take the lock early (before calling
+		// BackupAccountControl::CreateAccount) and silence the exception warning while we
+		// do so.
+		HideSpecificExceptionGuard guard(RaidFileException::ExceptionType,
+			RaidFileException::RaidFileDoesntExist);
+		mapFileSystem->GetLock();
+	}
+
 	BackupAccountControl::CreateAccount(mAccountID, SoftLimit, HardLimit, "");
 
 	BOX_NOTICE("Account " << BOX_FORMAT_ACCOUNT(mAccountID) << " created.");
@@ -595,6 +608,17 @@ int S3BackupAccountControl::CreateAccount(const std::string& name, int32_t SoftL
 		}
 	}
 
+	{
+		// Taking the lock will try to GetAccountIdentifier() (for the log message) which
+		// will throw a RaidFileException(RaidFileDoesntExist) because the BackupStoreInfo
+		// file does not exist yet. We expect that! So take the lock early (before calling
+		// BackupAccountControl::CreateAccount) and silence the exception warning while we
+		// do so.
+		HideSpecificExceptionGuard guard(HTTPException::ExceptionType,
+			HTTPException::FileNotFound);
+		mapFileSystem->GetLock();
+	}
+
 	// Create the BackupStoreInfo and BackupStoreRefCountDatabase files:
 	BackupAccountControl::CreateAccount(S3_FAKE_ACCOUNT_ID, SoftLimit, HardLimit, name);