This reduces some of the overhead caused by many concurrent fileclient
requests from minions.
Additionally, initializing remotes has been folded into the GitBase
class' dunder init. Instantiating an instance and initializing its
remotes were initially split so that an object could simply be created
with the master opts so that the configuration was loaded and nothing
else, allowing for certain cases (like clearing the cache files) where
we didn't need to actually initialize the remotes. But this both A)
presents a problem when the instance being used is a singleton, as you
don't want to be re-initializing the remotes all the time, and B)
suppressing initialization can be (and is now being) done via a new
argument to the dunder init.
This makes the following changes:
1. Renames the valid_providers param in GitBase to git_providers,
allowing for a dictionary mapping provider names to their associated
classes. This allows for alternate providers to be used with a
GitBase subclass.
2. Renames the get_provider function to verify_provider to reduce
confusion with git_providers.
3. Uses super() to run a parent class' dunder init instead of invoking
the parent class directly.
