[Forced commit to add log message that I fat-fingered last time]
[Forced commit to add log message that I fat-fingered last time]

Give a more reasonable error message when lock file exists but has
zero length; prior code confused this with could-not-read-file case.

royc1/gpdb,ahachete/gpdb,chrishajas/gpdb,rvs/gpdb,kmjungersen/PostgresXL,randomtask1155/gpdb,adam8157/gpdb,Quikling/gpdb,randomtask1155/gpdb,xuegang/gpdb,chrishajas/gpdb,postmind-net/postgres-xl,xinzweb/gpdb,yazun/postgres-xl,edespino/gpdb,foyzur/gpdb,randomtask1155/gpdb,janebeckman/gpdb,chrishajas/gpdb,ashwinstar/gpdb,0x0FFF/gpdb,Chibin/gpdb,oberstet/postgres-xl,snaga/postgres-xl,zaksoup/gpdb,cjcjameson/gpdb,rubikloud/gpdb,rvs/gpdb,lisakowen/gpdb,xuegang/gpdb,kaknikhil/gpdb,arcivanov/postgres-xl,postmind-net/postgres-xl,50wu/gpdb,0x0FFF/gpdb,yazun/postgres-xl,yuanzhao/gpdb,adam8157/gpdb,janebeckman/gpdb,lintzc/gpdb,cjcjameson/gpdb,foyzur/gpdb,tangp3/gpdb,techdragon/Postgres-XL,kaknikhil/gpdb,snaga/postgres-xl,randomtask1155/gpdb,kmjungersen/PostgresXL,kaknikhil/gpdb,rvs/gpdb,Postgres-XL/Postgres-XL,kaknikhil/gpdb,0x0FFF/gpdb,50wu/gpdb,randomtask1155/gpdb,foyzur/gpdb,tangp3/gpdb,zeroae/postgres-xl,lpetrov-pivotal/gpdb,CraigHarris/gpdb,zeroae/postgres-xl,0x0FFF/gpdb,yuanzhao/gpdb,lintzc/gpdb,oberstet/postgres-xl,50wu/gpdb,randomtask1155/gpdb,zaksoup/gpdb,zeroae/postgres-xl,royc1/gpdb,janebeckman/gpdb,royc1/gpdb,tangp3/gpdb,jmcatamney/gpdb,50wu/gpdb,zeroae/postgres-xl,techdragon/Postgres-XL,cjcjameson/gpdb,arcivanov/postgres-xl,Quikling/gpdb,xinzweb/gpdb,Quikling/gpdb,kaknikhil/gpdb,atris/gpdb,yazun/postgres-xl,tangp3/gpdb,xinzweb/gpdb,xuegang/gpdb,kmjungersen/PostgresXL,janebeckman/gpdb,lpetrov-pivotal/gpdb,adam8157/gpdb,lpetrov-pivotal/gpdb,tpostgres-projects/tPostgres,kaknikhil/gpdb,ashwinstar/gpdb,50wu/gpdb,tangp3/gpdb,techdragon/Postgres-XL,greenplum-db/gpdb,kaknikhil/gpdb,edespino/gpdb,cjcjameson/gpdb,edespino/gpdb,foyzur/gpdb,lisakowen/gpdb,adam8157/gpdb,lpetrov-pivotal/gpdb,Chibin/gpdb,janebeckman/gpdb,Quikling/gpdb,rvs/gpdb,royc1/gpdb,tpostgres-projects/tPostgres,foyzur/gpdb,foyzur/gpdb,yuanzhao/gpdb,pavanvd/postgres-xl,royc1/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,royc1/gpdb,adam8157/gpdb,CraigHarris/gpdb,rubikloud/gpdb,rubikloud/gpdb,CraigHarris/gpdb,arcivanov/postgres-xl,adam8157/gpdb,rubikloud/gpdb,kmjungersen/PostgresXL,xinzweb/gpdb,lisakowen/gpdb,zaksoup/gpdb,adam8157/gpdb,xuegang/gpdb,snaga/postgres-xl,ashwinstar/gpdb,lintzc/gpdb,kaknikhil/gpdb,edespino/gpdb,edespino/gpdb,rubikloud/gpdb,xuegang/gpdb,lpetrov-pivotal/gpdb,Postgres-XL/Postgres-XL,ahachete/gpdb,cjcjameson/gpdb,Postgres-XL/Postgres-XL,ahachete/gpdb,CraigHarris/gpdb,postmind-net/postgres-xl,yuanzhao/gpdb,rvs/gpdb,oberstet/postgres-xl,atris/gpdb,Quikling/gpdb,50wu/gpdb,tangp3/gpdb,lintzc/gpdb,greenplum-db/gpdb,royc1/gpdb,Quikling/gpdb,atris/gpdb,lisakowen/gpdb,chrishajas/gpdb,rubikloud/gpdb,jmcatamney/gpdb,Chibin/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,cjcjameson/gpdb,Quikling/gpdb,chrishajas/gpdb,lisakowen/gpdb,edespino/gpdb,zeroae/postgres-xl,edespino/gpdb,pavanvd/postgres-xl,chrishajas/gpdb,rvs/gpdb,lisakowen/gpdb,xinzweb/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,foyzur/gpdb,Quikling/gpdb,50wu/gpdb,CraigHarris/gpdb,lintzc/gpdb,janebeckman/gpdb,zaksoup/gpdb,Chibin/gpdb,janebeckman/gpdb,0x0FFF/gpdb,50wu/gpdb,Quikling/gpdb,greenplum-db/gpdb,lpetrov-pivotal/gpdb,jmcatamney/gpdb,atris/gpdb,postmind-net/postgres-xl,kmjungersen/PostgresXL,ovr/postgres-xl,ovr/postgres-xl,zaksoup/gpdb,greenplum-db/gpdb,CraigHarris/gpdb,rvs/gpdb,xuegang/gpdb,oberstet/postgres-xl,ashwinstar/gpdb,adam8157/gpdb,lisakowen/gpdb,postmind-net/postgres-xl,ahachete/gpdb,atris/gpdb,0x0FFF/gpdb,yuanzhao/gpdb,arcivanov/postgres-xl,janebeckman/gpdb,foyzur/gpdb,greenplum-db/gpdb,janebeckman/gpdb,xinzweb/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,lintzc/gpdb,rubikloud/gpdb,lintzc/gpdb,edespino/gpdb,oberstet/postgres-xl,janebeckman/gpdb,ovr/postgres-xl,zaksoup/gpdb,rvs/gpdb,kaknikhil/gpdb,ovr/postgres-xl,jmcatamney/gpdb,yuanzhao/gpdb,yazun/postgres-xl,edespino/gpdb,royc1/gpdb,chrishajas/gpdb,xuegang/gpdb,yuanzhao/gpdb,rvs/gpdb,atris/gpdb,Chibin/gpdb,yuanzhao/gpdb,ahachete/gpdb,Postgres-XL/Postgres-XL,randomtask1155/gpdb,Quikling/gpdb,ahachete/gpdb,rubikloud/gpdb,pavanvd/postgres-xl,atris/gpdb,snaga/postgres-xl,pavanvd/postgres-xl,ovr/postgres-xl,Postgres-XL/Postgres-XL,tangp3/gpdb,yazun/postgres-xl,cjcjameson/gpdb,tpostgres-projects/tPostgres,atris/gpdb,techdragon/Postgres-XL,tangp3/gpdb,ashwinstar/gpdb,ahachete/gpdb,zaksoup/gpdb,rvs/gpdb,chrishajas/gpdb,arcivanov/postgres-xl,ashwinstar/gpdb,cjcjameson/gpdb,lintzc/gpdb,CraigHarris/gpdb,0x0FFF/gpdb,xinzweb/gpdb,Chibin/gpdb,lpetrov-pivotal/gpdb,xuegang/gpdb,greenplum-db/gpdb,lisakowen/gpdb,randomtask1155/gpdb,edespino/gpdb,cjcjameson/gpdb,Chibin/gpdb,CraigHarris/gpdb,xinzweb/gpdb,yuanzhao/gpdb,tpostgres-projects/tPostgres,0x0FFF/gpdb,lintzc/gpdb,Chibin/gpdb,tpostgres-projects/tPostgres,lpetrov-pivotal/gpdb,CraigHarris/gpdb,zaksoup/gpdb,snaga/postgres-xl,cjcjameson/gpdb,kaknikhil/gpdb,xuegang/gpdb,Chibin/gpdb,ahachete/gpdb,arcivanov/postgres-xl,ashwinstar/gpdb,Chibin/gpdb