Bug 1276241

Description of problem:
when virt-who run at rhevm mode, unregister rhevh to satellite, virt-who will show "RestlibException: undefined method `inject' for nil:NilClass" in the process of reloading.

Version-Release number of selected component (if applicable):
subscription-manager-1.15.9-14.el7.x86_64
python-rhsm-1.15.4-5.el7.x86_64
virt-who-0.14-9.el7.noarch
vdsm-4.17.8-1.el7ev.noarch
Satellite-6.1.0-RHEL-7-20151027.0

How reproducible:
Always

Steps to Reproduce:
1. Register rhevh to satellite6.1, configure virt-who run at rhevm mode
[root@hp-z220-06 ~]# cat /etc/sysconfig/virt-who  | grep -v ^# | grep -v ^$
VIRTWHO_DEBUG=1
VIRTWHO_INTERVAL=5
VIRTWHO_RHEVM=1
VIRTWHO_RHEVM_OWNER=Default_Organization
VIRTWHO_RHEVM_ENV=Library
VIRTWHO_RHEVM_SERVER=https://10.66.79.8:443
VIRTWHO_RHEVM_USERNAME=admin@internal
VIRTWHO_RHEVM_PASSWORD=redhat
2. Start virt-who service, virt-who send h/g mapping to satellite
3. Unregister rhevh, then check virt-who's log
[root@hp-z220-06 ~]# subscription-manager  unregister
System has been unregistered.
[root@hp-z220-06 ~]# tail -f /var/log/rhsm/rhsm.log
2015-10-29 08:26:25,695 [WARNING]  @virtwho.py:357 - virt-who reload
2015-10-29 08:26:25,695 [DEBUG] subscription-manager:20497 @utils.py:284 - Restarted virt-who
2015-10-29 08:26:28,150 [ERROR]  @subscriptionmanager.py:171 - Communication with server failed:
Traceback (most recent call last):
  File "/usr/share/virt-who/manager/subscriptionmanager/subscriptionmanager.py", line 167, in hypervisorCheckIn
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 903, in hypervisorCheckIn
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 647, in request_post
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 564, in _request
  File "/usr/lib64/python2.7/site-packages/rhsm/connection.py", line 611, in validateResponse
RestlibException: undefined method `inject' for nil:NilClass
2015-10-29 08:26:28,150 [ERROR]  @virtwho.py:177 - Unable to send data: Communication with subscription manager failed with code 500: undefined method `inject' for nil:NilClass

Actual results:
It will show "RestlibException" when virt-who communicate with subscription manager.

Expected results:
vit-who shouldn't show "RestlibException" when communicate with subscription manager 

Additional info:
If virt-who run at vdsm mode, it hasn't this problem when unregister rhevh.