Correct failure modes when undefining VM

Undefining a VM would sometimes leave a remnant UUID in the
runningdomains list on the target hypervisor which persisted even
after restarting. This helps prevent that happening by splitting
the various undefine steps into separate try blocks, just in case
one fails.

Fixes #15

pvc.py

@@ -962,11 +962,8 @@ def undefine_vm(domain):
         dom_uuid = searchClusterByName(zk_conn, domain)
         dom_name = searchClusterByUUID(zk_conn, dom_uuid)
 
-    if dom_uuid == None:
-        click.echo('ERROR: Could not find VM "{}" in the cluster!'.format(domain))
-        stopZKConnection(zk_conn)
-        return
-
+    # Shut down the VM
+    try:
         current_vm_state = zk_conn.get('/domains/{}/state'.format(dom_uuid))[0].decode('ascii')
         if current_vm_state != 'stop':
             click.echo('Forcibly stopping VM "{}".'.format(dom_uuid))
@@ -978,12 +975,19 @@ def undefine_vm(domain):
             # Wait for 3 seconds to allow state to flow to all hypervisors
             click.echo('Waiting for cluster to update.')
             time.sleep(1)
+    except:
+        pass
 
     # Gracefully terminate the class instances
+    try:
         click.echo('Deleting VM "{}" from nodes.'.format(dom_uuid))
         zk_conn.set('/domains/{}/state'.format(dom_uuid), 'delete'.encode('ascii'))
         time.sleep(5)
+    except:
+        pass
+
     # Delete the configurations
+    try:
         click.echo('Undefining VM "{}".'.format(dom_uuid))
         transaction = zk_conn.transaction()
         transaction.delete('/domains/{}/state'.format(dom_uuid))
@@ -993,6 +997,8 @@ def undefine_vm(domain):
         transaction.delete('/domains/{}/xml'.format(dom_uuid))
         transaction.delete('/domains/{}'.format(dom_uuid))
         transaction.commit()
+    except:
+        pass
 
     # Close the Zookeeper connection
     stopZKConnection(zk_conn)