HBTU.waitUntilAllRegionsAssigned will count split/merged region and cause wait timeout

In TestTruncateTableProcedure, we will call split and then wait until all regions are assigned. The code itself is a bit strange and should be reimplement with other another way, but it expose the problem in our HBTU.waitUntilAllRegionsAssigned method, that we will also count split region, and find that it is not OPEN and return false, which causes a wait timeout.

This is the log.

https://builds.apache.org/job/HBase-Flaky-Tests/job/master/143/artifact/hbase-server/target/surefire-reports/org.apache.hadoop.hbase.master.procedure.TestTruncateTableProcedure-output.txt

Will open another issue to rewrite the test first, but I still think we need to open a issue to record this problem.