Description of problem:
When add/delete/migrate guests, the virt-who can't listen the events, and does not send the updates to SAM server. But it can send the current host/guest uuids info to SAM server if restart the virt-who service.

Version-Release number of selected component (if applicable):
virt-who-0.7-2.el5
subscription-manager-firstboot-1.0.13-1.el5
subscription-manager-1.0.13-1.el5
subscription-manager-gui-1.0.13-1.el5
python-rhsm-1.0.5-1.el5
katello-headpin-all-0.2.13-1.el6_2.noarch
candlepin-0.6.5-1.el6_2.noarch
ESX 5.0

How reproducible:

100%

Steps to Reproduce:
1. Config the virt-who config file
   # vi /etc/sysconfig/virt-who
    VIRTWHO_BACKGROUND=1 (enable debugging)
    VIRTWHO_DEBUG=1 (run in background)
    VIRTWHO_ESX=1
    VIRTWHO_ESX_OWNER=$OWNER
    VIRTWHO_ESX_ENV=$ENV
    VIRTWHO_ESX_SERVER=$IP
    VIRTWHO_ESX_USERNAME=Administrator
    VIRTWHO_ESX_PASSWORD=123qweP  
2. Start virt-who service
[root@localhost sysconfig]# service virt-who restart
Stopping virt-who:                                         [  OK  ]
Starting virt-who:                                         [  OK  ]
[root@localhost sysconfig]# /usr/lib64/python2.4/site-packages/rhsm/certificate.py:123: DeprecationWarning: Call to deprecated function: __init__
  category=DeprecationWarning)

3. Check the log in /var/log/rhsm/rhsm.log
# tail -f /var/log/rhsm/rhsm.log
...
2013-01-14 00:50:34,734 [WARNING]  @virt-who.py:413 - Listening for events is not available in VDSM or ESX mode
2013-01-14 00:50:39,528 [DEBUG]  @virt-who.py:428 - Virt-who is running in esx mode
2013-01-14 00:50:39,528 [DEBUG]  @virt-who.py:435 - Starting infinite loop with 3600 seconds interval and event handling
2013-01-14 00:50:40,852 [DEBUG]  @subscriptionmanager.py:89 - Sending update in hosts-to-guests mapping: {44454c4c-4c00-1031-8053-b8c04f4e3258: [422105c6-a599-939a-2c68-e93f3094c4d1], 44454c4c-4200-1034-8039-b8c04f503258: [422100fe-0e0c-477d-2638-a1f114e12ed1, 4221fd54-68f9-52ad-7ab9-0b7a7939ce7d]}
2013-01-14 00:50:41,103 [INFO]  @virt-who.py:197 - Updated host: 44454c4c-4c00-1031-8053-b8c04f4e3258 with guests: [422105c6-a599-939a-2c68-e93f3094c4d1]
2013-01-14 00:50:41,103 [INFO]  @virt-who.py:197 - Updated host: 44454c4c-4200-1034-8039-b8c04f503258 with guests: [422100fe-0e0c-477d-2638-a1f114e12ed1, 4221fd54-68f9-52ad-7ab9-0b7a7939ce7d]

4. Add/delete/migration guests, and check the log in /var/log/rhsm/rhsm.log.

 # tail -f /var/log/rhsm/rhsm.log
...
2013-01-14 00:50:34,734 [WARNING]  @virt-who.py:413 - Listening for events is not available in VDSM or ESX mode
2013-01-14 00:50:39,528 [DEBUG]  @virt-who.py:428 - Virt-who is running in esx mode
2013-01-14 00:50:39,528 [DEBUG]  @virt-who.py:435 - Starting infinite loop with 3600 seconds interval and event handling
2013-01-14 00:50:40,852 [DEBUG]  @subscriptionmanager.py:89 - Sending update in hosts-to-guests mapping: {44454c4c-4c00-1031-8053-b8c04f4e3258: [422105c6-a599-939a-2c68-e93f3094c4d1], 44454c4c-4200-1034-8039-b8c04f503258: [422100fe-0e0c-477d-2638-a1f114e12ed1, 4221fd54-68f9-52ad-7ab9-0b7a7939ce7d]}
2013-01-14 00:50:41,103 [INFO]  @virt-who.py:197 - Updated host: 44454c4c-4c00-1031-8053-b8c04f4e3258 with guests: [422105c6-a599-939a-2c68-e93f3094c4d1]
2013-01-14 00:50:41,103 [INFO]  @virt-who.py:197 - Updated host: 44454c4c-4200-1034-8039-b8c04f503258 with guests: [422100fe-0e0c-477d-2638-a1f114e12ed1, 4221fd54-68f9-52ad-7ab9-0b7a7939ce7d]

 ^^^^^^^^^^There are no changes.

  
Actual results:
When add/delete/migration guests, the virt-who can't listening the events, and does not send the updates to SAM server.

Expected results:
When add/delete/migration guests, the virt-who can send the updates to SAM server.

Additional info:
If restart the virt-who service, virt-who can report the correct host/guest uuids info.