merge SytzeH: Run optional configuration script before starting service
merge SytzeH: Run optional configuration script before starting service

Merge pull request #1498 from SytzeH/sql-layer/startupConfigCentos
https://github.com/FoundationDB/sql-layer/pull/1498

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