Revert "Merge pull request #598 from blueboxgroup/backport-1.0.x-glance-store-check"

sensu_check prefix flag doesn't work as intended, it yields a sensu
config like this:
```
"command": "sudo . /root/stackrc;
GLANCE_IMAGE_DIR=/var/lib/glance/images
/etc/sensu/plugins/check-glance-store.py ",
```
Where we need to use sudo to access /root/stackrc and
/var/lib/glance/images but sudo can't execute bash builtin . and
check-glance-store.py isn't invoked as root.

This reverts commit 2cd9ac7ac97792c1c9c14c7f0ff04129ca684f1f, reversing
changes made to 57b6be2987a4597f3fc6f5edb80b298cca02c2f3.