Major Description
Because we are going to upgrade the HBase kernel version, during the test, I found that the HMaster ShutdownHook of version 1.7.1 and 2.4.9 did not take effect if tablesOnMaster is false. After further confirmation, I found that all versions of HBase 1.x and 2.x have this problem.
I analyzed the cause of the problem：
Before HBase 3.x, HMaster registered ShutdownHook by calling the run() method of HRegionServer, but the run() method will be blocked on the waitForMasterActive() method of HMaster(before registering the shutdownhook) if tablesOnMaster is false. Eventually, the ShutdownHook of HMaster was not registered successfully.
1. The code path of HRegionServer's run() method：
2. The preRegistrationInitialization() method will be called first:
3. The HMaster's waitForMasterActive() method will be blocked if tablesOnMaster is false:
Finally, because the default value of tablesOnMaster is false, the ShutdownHook of HMaster was not registered successfully.
