pgsql: Update HINT for pre-existing shared memory block.

Update HINT for pre-existing shared memory block.

One should almost always terminate an old process, not use a manual
removal tool like ipcrm.  Removal of the ipcclean script eleven years
ago (39627b1ae680cba44f6e56ca5facec4fdbfe9495) and its non-replacement
corroborate that manual shm removal is now a niche goal.  Back-patch to
9.4 (all supported versions).

Reviewed by Daniel Gustafsson and Kyotaro HORIGUCHI.

Discussion: https://postgr.es/m/20180812064815.GB2301738@rfd.leadboat.com

Branch
------
REL_10_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/327399412d035a3951f48d74356ff1449b9b7e91

Modified Files
--------------
src/backend/utils/init/miscinit.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)