__LiquigraphLock is left in place whenever migration / changset fails.
Here's an excerpt from the log:
```
Cannot remove __LiquigraphLock during cleanup.
java.sql.SQLException: org.neo4j.driver.v1.exceptions.ClientException: Cannot run more statements in this transaction, because previous statements in the transaction has failed and the transaction has been rolled back. Please start a new transaction to run another statement.
at org.neo4j.jdbc.bolt.BoltNeo4jPreparedStatement.executeInternal(BoltNeo4jPreparedStatement.java:105) ~[neo4j-jdbc-driver-3.3.1.jar!/:na]
at org.neo4j.jdbc.bolt.BoltNeo4jPreparedStatement.execute(BoltNeo4jPreparedStatement.java:77) ~[neo4j-jdbc-driver-3.3.1.jar!/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0181]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0181]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0181]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0181]
at org.neo4j.jdbc.utils.Neo4jInvocationHandler.invoke(Neo4jInvocationHandler.java:54) ~[neo4j-jdbc-driver-3.3.1.jar!/:na]
at com.sun.proxy.$Proxy223.execute(Unknown Source) ~[na:na]
at org.liquigraph.core.io.lock.LiquigraphLock.releaseLock(LiquigraphLock.java:123) [liquigraph-core-3.0.2.jar!/:na]
at org.liquigraph.core.io.lock.LiquigraphLock.release(LiquigraphLock.java:54) [liquigraph-core-3.0.2.jar!/:na]
at org.liquigraph.core.io.lock.LockableConnection.close(LockableConnection.java:103) [liquigraph-core-3.0.2.jar!/:na]
at org.liquigraph.core.api.MigrationRunner.runMigrations(MigrationRunner.java:81) [liquigraph-core-3.0.2.jar!/:na]
at org.liquigraph.core.api.Liquigraph.runMigrations(Liquigraph.java:63) [liquigraph-core-3.0.2.jar!/:na]
at org.liquigraph.spring.SpringLiquigraph.afterPropertiesSet(SpringLiquigraph.java:52) [liquigraph-spring-boot-starter-3.0.2.jar!/:na]
at
```
To reproduce this, create changeset that fails (for example, create an invalid query).
This was observed in a Spring Boot application, using org.liquigraph:liquigraph-spring-boot-starter:3.0.2.