private InternalDistributedMember getExistingPrimary() {
    return basicGetPrimaryMember();
  }
This method was split out from getPrimary() due to bug #40639 and is only intended to be called
from within that method.

@see #getPrimary()
@return the existing primary (if it is still in the view) otherwise null
geode-core/src/main/java/org/apache/geode/internal/cache/BucketAdvisor.java