pgsql: Follow-up fixes for "Make all Perl warnings fatal"

Follow-up fixes for "Make all Perl warnings fatal"

Mostly, we need to check whether $ENV{PG_TEST_EXTRA} is set before
doing regular expression matches against it.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/9d49837d7144e27ad8ea8918acb28f9872cb1585

Modified Files
--------------
src/interfaces/libpq/t/004_load_balance_dns.pl                  | 2 +-
src/test/kerberos/t/001_auth.pl                                 | 4 ++--
src/test/ldap/t/001_auth.pl                                     | 2 +-
src/test/ldap/t/002_bindpasswd.pl                               | 2 +-
src/test/modules/ldap_password_func/t/001_mutated_bindpasswd.pl | 2 +-
src/test/modules/xid_wraparound/t/001_emergency_vacuum.pl       | 2 +-
src/test/modules/xid_wraparound/t/002_limits.pl                 | 2 +-
src/test/modules/xid_wraparound/t/003_wraparounds.pl            | 2 +-
src/test/ssl/t/001_ssltests.pl                                  | 2 +-
src/test/ssl/t/002_scram.pl                                     | 2 +-
src/test/ssl/t/003_sslinfo.pl                                   | 2 +-
11 files changed, 12 insertions(+), 12 deletions(-)