Richer information to indicate the place where swith-to-slave even is cancelled.
Merge pull request #3442 from S124568/2.1-null-uri-msg-in-cluster

Richer information to indicate the place where swith-to-slave even is ca...
Merge branch '2.1-maint'

Conflicts:
	enterprise/ha/src/main/java/org/neo4j/kernel/ha/cluster/HighAvailabilityModeSwitcher.java
	enterprise/ha/src/main/java/org/neo4j/kernel/ha/cluster/SwitchToSlave.java
Merge pull request #3500 from digitalstain/master

Merge branch 2.1-maint into master