bug fix: rename accelerator to Accelerator

When run:
$ python -m unittest cyborg.tests.unit.accelerator.drivers.modules.test_generic

It will report the follow error:
  File "cyborg/tests/unit/accelerator/drivers/modules/test_generic.py", line 20, in <module>
    from cyborg.accelerator.drivers.generic_driver import GenericDriver as generic
  File "cyborg/accelerator/drivers/generic_driver.py", line 24, in <module>
    from cyborg.accelerator import accelerator
  File "cyborg/accelerator/accelerator.py", line 23, in <module>
    class accelerator(Base):
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/api.py", line 64, in __init__
    _as_declarative(cls, classname, cls.__dict__)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/base.py", line 88, in _as_declarative
    _MapperConfig.setup_mapping(cls, classname, dict_)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/base.py", line 103, in setup_mapping
    cfg_cls(cls_, classname, dict_)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/base.py", line 125, in __init__
    clsregistry.add_class(self.classname, self.cls)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/clsregistry.py", line 65, in add_class
    module.add_class(classname, cls)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/clsregistry.py", line 172, in add_class
    existing.add_item(cls)
AttributeError: '_ModuleMarker' object has no attribute 'add_item'

That's because:
_ModuleMarker will add the module name and class name in to same contents dict.
_MultipleClassMarker refers to multiple classes of the same name within _decl_class_registry.
It has add_item attribute.
_ModuleMarker refers to a module name within _decl_class_registry.
It does not have add_item attribute.

So the class name should be different with module name.

REF:
https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/ext/declarative/clsregistry.py

Change-Id: I8d8aa8809f6afd5b9eaace832a06ba7f3770e652

cyborg/accelerator/accelerator.py

@@ -20,7 +20,7 @@ Base = declarative_base()
 
 
 # A common internal acclerator object for internal use.
-class accelerator(Base):
+class Accelerator(Base):
     __tablename__ = 'accelerators'
     accelerator_id = Column(String, primary_key=True)
     device_type = Column(String)

cyborg/accelerator/drivers/generic_driver.py

@@ -44,7 +44,7 @@ class GenericDriver(generic.GENERICDRIVER):
     def do_setup(self, context):
         """Any initialization the generic driver does while starting."""
         super(GenericDriver, self).do_setup(context)
-        self.acc = accelerator.accelerator()
+        self.acc = accelerator.Accelerator()
 
     def create_accelerator(self, context):
         """Creates accelerator."""