pgsql: Handle invalid libpq sockets in more places

Handle invalid libpq sockets in more places

Also, make error messages consistent.

From: Michael Paquier <michael.paquier@gmail.com>

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/a40814d7aacbda9266c703cc011d3506668899de

Modified Files
--------------
.../replication/libpqwalreceiver/libpqwalreceiver.c       |  2 +-
src/bin/pg_basebackup/pg_recvlogical.c                    |  8 ++++++++
src/bin/pg_basebackup/receivelog.c                        |  3 ++-
src/bin/pgbench/pgbench.c                                 |  5 +++--
src/bin/scripts/vacuumdb.c                                | 15 +++++++++++----
src/interfaces/libpq/fe-misc.c                            |  2 +-
src/test/isolation/isolationtester.c                      |  6 ++++++
7 files changed, 32 insertions(+), 9 deletions(-)