Log deletion errors in  clean servers

Although we don't want to cause tempest to fail on error while deleting
a server in tearDownClass as these types of issues are hard to debug. We
should at least log the issues instead of hiding them completely.

Change-Id: Id0c172e247ecfcd4eec85bafd4787e33944cee1a
Related-Bug: #1372696
Add "reboot_instance" EC2 API test

Currently, in "tempest/thirdparty/boto/test_ec2_instance_run.py",
no test case present to test the "reboot_instance" api, similar
to stop_instance, terminate_instance, etc.

Closes-Bug: #1352341

Change-Id: Ifbd8607566961dbf32b40f34ff603f712d856f6a
Merge "Log deletion errors in  clean servers"
Merge "Add "reboot_instance" EC2 API test"
Merge branch 'master' of https://github.com/openstack/tempest