merge nathanlws: Add external config path in test policy
merge nathanlws: Add external config path in test policy

Merge pull request #1681 from nathanlws/sql-layer/config-test-policy-path
https://github.com/FoundationDB/sql-layer/pull/1681

qiuyesuifeng/sql-layer,shunwang/sql-layer-1,ngaut/sql-layer,ngaut/sql-layer,ngaut/sql-layer,shunwang/sql-layer-1,wfxiang08/sql-layer-1,ngaut/sql-layer,wfxiang08/sql-layer-1,relateiq/sql-layer,shunwang/sql-layer-1,qiuyesuifeng/sql-layer,jaytaylor/sql-layer,qiuyesuifeng/sql-layer,qiuyesuifeng/sql-layer,wfxiang08/sql-layer-1,jaytaylor/sql-layer,shunwang/sql-layer-1,relateiq/sql-layer,relateiq/sql-layer,jaytaylor/sql-layer,jaytaylor/sql-layer,wfxiang08/sql-layer-1,relateiq/sql-layer