Remove TestModel default permissions

[aabharya]

Since default permissions for TestModel is not used in tests or views it would be nice to explicitly remove them so they don't show up in admin panel.
Currently installing health_check.db in INSTALLED_APPS adds 4 default permissions and shows them in admin panel with somehow generic yet ambiguous names:

db | test model | Can view test model
db | test model | Can add test model
db | test model | Can change test model
db | test model | Can delete test model

[frankwiles]

Oh yeah that's a good idea for sure.

[aabharya]

@frankwiles I have prepared #451 to address this issue.