Improve reporting of error situations in find_other_exec().
Improve reporting of error situations in find_other_exec().

This function suppressed any stderr output from the called program, which
is unnecessary in the normal case and unhelpful in error cases.  It also
gave a rather opaque message along the lines of "fgets failure: Success"
in case the called program failed to return anything on stdout.  Since
we've seen multiple reports of people not understanding what's wrong when
pg_ctl reports this, improve the message.

Back-patch to all active branches.

greenplum-db/gpdb,rvs/gpdb,chrishajas/gpdb,50wu/gpdb,lisakowen/gpdb,jmcatamney/gpdb,lisakowen/gpdb,janebeckman/gpdb,xuegang/gpdb,Quikling/gpdb,xinzweb/gpdb,adam8157/gpdb,jmcatamney/gpdb,rvs/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,lintzc/gpdb,janebeckman/gpdb,kaknikhil/gpdb,xinzweb/gpdb,adam8157/gpdb,greenplum-db/gpdb,janebeckman/gpdb,adam8157/gpdb,rvs/gpdb,lintzc/gpdb,ahachete/gpdb,CraigHarris/gpdb,royc1/gpdb,ashwinstar/gpdb,50wu/gpdb,royc1/gpdb,royc1/gpdb,CraigHarris/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb,chrishajas/gpdb,edespino/gpdb,zaksoup/gpdb,janebeckman/gpdb,yuanzhao/gpdb,lisakowen/gpdb,greenplum-db/gpdb,xuegang/gpdb,Quikling/gpdb,xuegang/gpdb,xinzweb/gpdb,yuanzhao/gpdb,kaknikhil/gpdb,lintzc/gpdb,ashwinstar/gpdb,Chibin/gpdb,ahachete/gpdb,greenplum-db/gpdb,kaknikhil/gpdb,ashwinstar/gpdb,50wu/gpdb,yuanzhao/gpdb,xinzweb/gpdb,kaknikhil/gpdb,adam8157/gpdb,cjcjameson/gpdb,edespino/gpdb,Quikling/gpdb,greenplum-db/gpdb,50wu/gpdb,ahachete/gpdb,adam8157/gpdb,kaknikhil/gpdb,edespino/gpdb,yuanzhao/gpdb,janebeckman/gpdb,jmcatamney/gpdb,Chibin/gpdb,adam8157/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,rvs/gpdb,royc1/gpdb,lisakowen/gpdb,kaknikhil/gpdb,Chibin/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,janebeckman/gpdb,CraigHarris/gpdb,yuanzhao/gpdb,zaksoup/gpdb,xuegang/gpdb,janebeckman/gpdb,cjcjameson/gpdb,edespino/gpdb,Quikling/gpdb,ahachete/gpdb,adam8157/gpdb,Quikling/gpdb,royc1/gpdb,Chibin/gpdb,greenplum-db/gpdb,Chibin/gpdb,yuanzhao/gpdb,xuegang/gpdb,cjcjameson/gpdb,zaksoup/gpdb,0x0FFF/gpdb,rvs/gpdb,0x0FFF/gpdb,xinzweb/gpdb,0x0FFF/gpdb,zaksoup/gpdb,xuegang/gpdb,royc1/gpdb,greenplum-db/gpdb,xinzweb/gpdb,yuanzhao/gpdb,ahachete/gpdb,yuanzhao/gpdb,edespino/gpdb,cjcjameson/gpdb,lisakowen/gpdb,chrishajas/gpdb,ashwinstar/gpdb,zaksoup/gpdb,janebeckman/gpdb,ahachete/gpdb,royc1/gpdb,0x0FFF/gpdb,CraigHarris/gpdb,cjcjameson/gpdb,edespino/gpdb,CraigHarris/gpdb,xinzweb/gpdb,xuegang/gpdb,lisakowen/gpdb,0x0FFF/gpdb,lintzc/gpdb,Chibin/gpdb,Quikling/gpdb,zaksoup/gpdb,Quikling/gpdb,kaknikhil/gpdb,rvs/gpdb,lintzc/gpdb,ahachete/gpdb,lintzc/gpdb,cjcjameson/gpdb,rvs/gpdb,zaksoup/gpdb,Chibin/gpdb,lintzc/gpdb,50wu/gpdb,edespino/gpdb,chrishajas/gpdb,Chibin/gpdb,royc1/gpdb,janebeckman/gpdb,lintzc/gpdb,CraigHarris/gpdb,ashwinstar/gpdb,chrishajas/gpdb,chrishajas/gpdb,xuegang/gpdb,Quikling/gpdb,CraigHarris/gpdb,lintzc/gpdb,kaknikhil/gpdb,zaksoup/gpdb,Chibin/gpdb,ashwinstar/gpdb,50wu/gpdb,jmcatamney/gpdb,Quikling/gpdb,chrishajas/gpdb,rvs/gpdb,ashwinstar/gpdb,lisakowen/gpdb,Chibin/gpdb,50wu/gpdb,chrishajas/gpdb,0x0FFF/gpdb,0x0FFF/gpdb,rvs/gpdb,jmcatamney/gpdb,kaknikhil/gpdb,CraigHarris/gpdb,0x0FFF/gpdb,yuanzhao/gpdb,lisakowen/gpdb,jmcatamney/gpdb,janebeckman/gpdb,jmcatamney/gpdb,kaknikhil/gpdb,CraigHarris/gpdb,cjcjameson/gpdb,edespino/gpdb,edespino/gpdb,adam8157/gpdb,ahachete/gpdb,Quikling/gpdb,rvs/gpdb,edespino/gpdb,xuegang/gpdb