Fix a regression in the performance tests causing the db key to be regenerated everytime.

bramble-core/src/test/java/org/briarproject/bramble/db/DatabasePerformanceComparisonTest.java

 package org.briarproject.bramble.db;
 
+import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.system.Clock;
@@ -26,6 +27,7 @@ public abstract class DatabasePerformanceComparisonTest
 	 * How many blocks of each condition to compare.
 	 */
 	private static final int COMPARISON_BLOCKS = 10;
+	private SecretKey databaseKey = getSecretKey();
 
 	abstract Database<Connection> createDatabase(boolean conditionA,
 			DatabaseConfig databaseConfig, Clock clock);
@@ -72,7 +74,7 @@ public abstract class DatabasePerformanceComparisonTest
 			throws DbException {
 		Database<Connection> db = createDatabase(conditionA,
 				new TestDatabaseConfig(testDir, MAX_SIZE), new SystemClock());
-		db.open(getSecretKey(), null);
+		db.open(databaseKey, null);
 		return db;
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseTraceTest.java

 package org.briarproject.bramble.db;
 
+import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.system.Clock;
@@ -20,6 +21,8 @@ import static org.briarproject.bramble.test.TestUtils.getSecretKey;
 
 public abstract class DatabaseTraceTest extends DatabasePerformanceTest {
 
+	private SecretKey databaseKey = getSecretKey();
+
 	abstract Database<Connection> createDatabase(DatabaseConfig databaseConfig,
 			Clock clock);
 
@@ -44,7 +47,7 @@ public abstract class DatabaseTraceTest extends DatabasePerformanceTest {
 	private Database<Connection> openDatabase() throws DbException {
 		Database<Connection> db = createDatabase(
 				new TestDatabaseConfig(testDir, MAX_SIZE), new SystemClock());
-		db.open(getSecretKey(), null);
+		db.open(databaseKey, null);
 		return db;
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/db/SingleDatabasePerformanceTest.java

 package org.briarproject.bramble.db;
 
+import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.system.Clock;
@@ -22,6 +23,8 @@ public abstract class SingleDatabasePerformanceTest
 	abstract Database<Connection> createDatabase(DatabaseConfig databaseConfig,
 			Clock clock);
 
+	private SecretKey databaseKey = getSecretKey();
+
 	@Override
 	protected void benchmark(String name,
 			BenchmarkTask<Database<Connection>> task) throws Exception {
@@ -41,7 +44,7 @@ public abstract class SingleDatabasePerformanceTest
 	private Database<Connection> openDatabase() throws DbException {
 		Database<Connection> db = createDatabase(
 				new TestDatabaseConfig(testDir, MAX_SIZE), new SystemClock());
-		db.open(getSecretKey(), null);
+		db.open(databaseKey, null);
 		return db;
 	}