title: Aerospike asbackup command generates invalid namespace error
body: <p>To backup data from test namespace in Aerospike database to current directory, the following asbackup command generates an invalid namespace error. </p>
  
  <p>There is the test namespace and employee set in it with few records. I can read and write the records using golang driver. Is there any configuration required for asbackup?</p>
  
  <pre><code>asbackup --host 172.28.128.3:3000 --namespace test  --directory .
  </code></pre>
  
  <p>Error is:</p>
  
  <pre><code>2020-02-11 16:48:32 UTC [INF] [88270] Starting 100% backup of 172.28.128.3:3000 
  (namespace: test, set: [all], bins: [all], after: [none], before: [none]) to .
  2020-02-11 16:48:32 UTC [INF] [88270] [src/main/aerospike/as_cluster.c:124] 
  [as_cluster_add_nodes_copy] Add node BB949C170270008 172.28.128.3:3000
  2020-02-11 16:48:32 UTC [INF] [88270] Processing 1 node(s)
  2020-02-11 16:48:32 UTC [INF] [88270] Node ID Objects Replication    
  2020-02-11 16:48:32 UTC [ERR] [88270] Invalid namespace test
  2020-02-11 16:48:32 UTC [ERR] [88270] Error while counting cluster objects
  </code></pre>
  
  <p>Using MacOs 10.15.3; Aerospike Backup Utility Version 3.2.3; C Client Version 4.2.0;
  Aerospike running on docker 2.2.0.3</p>