Improve XTS Api for looking up Recovery Manager to prevent developer from poling

Currently the developer needs to poll for the RecoveryManager as it's possible that the application can be deployed before the XTS subsystem has finished startup.

This issue was worked around in JBTM-1522 and in the TXBridge tests, by having the application poll until the RM was not null.

Two possible solutions:

Have a blocking call to XTSATRecoveryManager.getRecoveryManager() that doesn't return until there is an RM available. if we use the existing java method, we need to analyse all usages to make sure returning null is not a valid outcome.

Another solution is to find out how to delay the application's initialisation until after XTS has started. This puts the burden on the application developer to implement, but requires no changes to the XTS code. See JBTM-1522 for alternative mechanisms for initialising the application. I tried three and none of them fired after the server had booted.

To Reproduce

Put breakpoints on:

Application's usage of: XTSATRecoveryManager.getRecoveryManager(); //Stop all threads
XTSATRecoveryManager.setRecoveryManager() // stop on Thread only

Copy your application to the deploy directory (xtstest.war is a good choice). Now start the server with debugging enabled (suspend=y). To reproduce this you will see the XTSATRecoveryManager.setRecoveryManager() BP fire, and then shortly after the XTSATRecoveryManager.getRecoveryManager() BP will fire. Allow the getRecoveryManager to continue and you will notice it is null. Fix this problem, and the getRecoveryManager will wait until the setRecoveryManager is complete and thus always return a non-null RM.

Once this is fixed, find all occurrence of the polling work-around and have them use the solution to this issue.