Existance of node/rel is checked before deletion
Merge pull request #3697 from lutovich/2.1-double-delete-of-rel-rollbacks-tx

Existance of node/rel is checked before deletion
Merge 2.1-maint in master

Conflicts:
	community/kernel/src/main/java/org/neo4j/kernel/impl/api/LockingStatementOperations.java
	community/kernel/src/main/java/org/neo4j/kernel/impl/api/StateHandlingStatementOperations.java
	community/kernel/src/main/java/org/neo4j/kernel/impl/api/store/CacheLayer.java
	community/kernel/src/main/java/org/neo4j/kernel/impl/api/store/PersistenceCache.java