Silence compiler warning about using too small a buffer.
Silence compiler warning about using too small a buffer.

resgroup-ops-linux.c: In function ‘removeDir’:
resgroup-ops-linux.c:652:17: warning: ‘%ld’ directive writing between 1 and 20 bytes into a region of size 16 [-Wformat-overflow=]
   sprintf(str, "%ld", pid);
                 ^~~
resgroup-ops-linux.c:652:16: note: directive argument in the range [-9223372036854775808, 9223372036854775806]
   sprintf(str, "%ld", pid);
                ^~~~~
resgroup-ops-linux.c:652:3: note: ‘sprintf’ output between 2 and 21 bytes into a destination of size 16
   sprintf(str, "%ld", pid);
   ^~~~~~~~~~~~~~~~~~~~~~~~

That couldn't overflow in reality, because a pid cannot be that large,
but let's avoid the warning.

jmcatamney/gpdb,greenplum-db/gpdb,xinzweb/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,xinzweb/gpdb,50wu/gpdb,greenplum-db/gpdb,50wu/gpdb,ashwinstar/gpdb,adam8157/gpdb,50wu/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,greenplum-db/gpdb,50wu/gpdb,jmcatamney/gpdb,xinzweb/gpdb,adam8157/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,adam8157/gpdb,ashwinstar/gpdb,lisakowen/gpdb,jmcatamney/gpdb,xinzweb/gpdb,jmcatamney/gpdb,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,ashwinstar/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,xinzweb/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,50wu/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,lisakowen/gpdb,adam8157/gpdb