XD-2041: Check asciidoc cross ref links
XD-2067 update asciidoctor toolchain
XD-2058: Renamed DeploymentVerifier

Renamed DeploymentVerifier to ResourceStateVerifier.

Added methods to SingleNodeIntegrationTestSupport to allow blocking
until incomplete status.
reverted to compile scope on 'spring-integration-groovy' for java 8 compiles
XD-2004: Containers stopped responding to Admin

Fixed race condition between the container creating the
/xd/deployments/modules/allocated/container-id path and the
supervisor removing the path when the container exits.
The container will now wait for the supervisor to remove
the path before proceeding with startup.

Added onSuspend and onResume to ZooKeeperConnectionListener.
This allows us to distinguish between events where container
ephemeral nodes need to be created after a network disconnect.

Temporary network disconnects will raise SUSPENDED events
followed by RECONNECTED events. Containers will now avoid
undeploying modules upon SUSPENDED events. LOST events still
cause modules to be undeployed. RECONNECTED events will
force a shutdown and recreation of the ZooKeeper client
if the prior event was LOST. If the prior event was
SUSPENDED, the container will re-register if the existing
ephemeral node for that container was created by the previous
ZooKeeper client session.

Testing was done on Linux via iptables DROP rules. Additionally,
testing was performed with a ZooKeeper ensemble, including
the shut down of 2 out of 3 servers to disrupt quorum.
XD-2047 Expose Redis Bus Headers Customization

JIRA: https://jira.spring.io/browse/XD-2047

The redis bus supports passing custom (string-valued) headers but
there was no easy way to configure them.

Add a property to `application.yml`, `servers.yml` to allow
customization.