Allow CheckpointManager init() and load() to use a different db type with path_prefix
Allow CheckpointManager init() and load() to use a different db type with path_prefix

Summary: CheckpointManager already accepts a path_prefix override for init() and load(), but it assumes the same db_type passed in __init__(). This change adds an optional path_type for each call.

Reviewed By: boryiingsu

Differential Revision: D5888152

fbshipit-source-id: 21cd31a62a0188fe0e0b19b43c3b232c2342d0a8

davinwang/caffe2,davinwang/caffe2,Yangqing/caffe2,caffe2/caffe2,davinwang/caffe2,pietern/caffe2,xzturn/caffe2,xzturn/caffe2,Yangqing/caffe2,davinwang/caffe2,pietern/caffe2,Yangqing/caffe2,sf-wind/caffe2,sf-wind/caffe2,sf-wind/caffe2,sf-wind/caffe2,xzturn/caffe2,pietern/caffe2,pietern/caffe2,davinwang/caffe2,Yangqing/caffe2,sf-wind/caffe2,pietern/caffe2,Yangqing/caffe2,xzturn/caffe2,xzturn/caffe2