Add unit test for LUGroupVerifyDisks
Add unit test for LUGroupVerifyDisks

This patch adds unit test coverage for LUGroupVerifyDisks.

Signed-off-by: Thomas Thrainer <98bdeac947eb8ca18146e9ce7f092788ec242cd1@google.com>
Reviewed-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>

onponomarev/ganeti,bitemyapp/ganeti,ganeti/ganeti,dimara/ganeti,grnet/snf-ganeti,bitemyapp/ganeti,onponomarev/ganeti,ganeti-github-testing/ganeti-test-1,leshchevds/ganeti,ganeti/ganeti,yiannist/ganeti,grnet/snf-ganeti,mbakke/ganeti,ganeti-github-testing/ganeti-test-1,leshchevds/ganeti,apyrgio/snf-ganeti,apyrgio/snf-ganeti,apyrgio/ganeti,apyrgio/ganeti,leshchevds/ganeti,mbakke/ganeti,andir/ganeti,andir/ganeti,andir/ganeti,mbakke/ganeti,yiannist/ganeti,yiannist/ganeti,ganeti/ganeti,dimara/ganeti