Don't exit from the Canary daemon mode if no regions are present

Using the regionserver mode the canary exit if there are no region servers

hbase o.a.h.h.tool.Canary -daemon -regionserver REGION_NAME

while in table mode the canary is waiting until the table is up

hbase o.a.h.h.tool.Canary -daemon TABLE_NAME

Remove the exit code from the region server mode, and keep waiting until the -t timeout or the region shows up