If a configuration file can't be loaded, show which one
If a configuration file can't be loaded, show which one

So far the error message only says it can't be loaded, but not what file
it is.

Signed-off-by: Petr Pudlak <9d19625f8ee825a2c398462ed335cbcf98f79c32@google.com>
Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>

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