HBASE-22874 Define a public API for Canary checking and a non-public tool implementation

Closes #580

* Canary is now an IA.Public interface
* CanaryTool is now the implementation

Signed-off-by: Sean Busbey <busbey@apache.org>
(cherry picked from commit b5a3967)

Author: Rushabh

bin/hbase

@@ -607,7 +607,7 @@ elif [ "$COMMAND" = "ltt" ] ; then
   CLASS='org.apache.hadoop.hbase.util.LoadTestTool'
   HBASE_OPTS="$HBASE_OPTS $HBASE_LTT_OPTS"
 elif [ "$COMMAND" = "canary" ] ; then
-  CLASS='org.apache.hadoop.hbase.tool.Canary'
+  CLASS='org.apache.hadoop.hbase.tool.CanaryTool'
   HBASE_OPTS="$HBASE_OPTS $HBASE_CANARY_OPTS"
 elif [ "$COMMAND" = "version" ] ; then
   CLASS='org.apache.hadoop.hbase.util.VersionInfo'

hbase-server/src/main/jamon/org/apache/hadoop/hbase/tmpl/master/MasterStatusTmpl.jamon

@@ -55,7 +55,7 @@ org.apache.hadoop.hbase.quotas.QuotaUtil;
 org.apache.hadoop.hbase.security.access.AccessControlLists;
 org.apache.hadoop.hbase.security.visibility.VisibilityConstants;
 org.apache.hadoop.hbase.shaded.protobuf.generated.SnapshotProtos.SnapshotDescription;
-org.apache.hadoop.hbase.tool.Canary;
+org.apache.hadoop.hbase.tool.CanaryTool;
 org.apache.hadoop.hbase.util.Bytes;
 org.apache.hadoop.hbase.util.FSUtils;
 org.apache.hadoop.hbase.util.JvmVersion;
@@ -444,7 +444,7 @@ AssignmentManager assignmentManager = master.getAssignmentManager();
     <%java>String description = null;
         if (tableName.equals(TableName.META_TABLE_NAME)){
             description = "The hbase:meta table holds references to all User Table regions.";
-        } else if (tableName.equals(Canary.DEFAULT_WRITE_TABLE_NAME)){
+        } else if (tableName.equals(CanaryTool.DEFAULT_WRITE_TABLE_NAME)){
             description = "The hbase:canary table is used to sniff the write availbility of"
               + " each regionserver.";
         } else if (tableName.equals(AccessControlLists.ACL_TABLE_NAME)){