Add multiple vms disk error_policy test cases.
Change unhotplug to coldplug.
Test shableable block disk on 2 domains.
Move some common functions to utils_test.libvirt.py
Change fs creation method to utils_test.libvirt.mkfs/mk_part.
Modify iscsi device creation method.
Fix a bug of report error policy.
Improved the code implementation.
Merge pull request #199 from rbian/error-policy

Add disk error_policy test cases.