pgsql: Prefix RLS regression test roles with 'regress_'

Prefix RLS regression test roles with 'regress_'

To avoid any possible overlap with existing roles on a system when
doing a 'make installcheck', use role names which start with
'regress_'.

Pointed out by Tom.

Branch
------
master

Details
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http://git.postgresql.org/pg/commitdiff/6c7b0388c568e3063c3d40a7d90e1bca9006d505

Modified Files
--------------
src/test/regress/expected/rowsecurity.out | 828 +++++++++++++++---------------
src/test/regress/sql/rowsecurity.sql      | 454 ++++++++--------
2 files changed, 641 insertions(+), 641 deletions(-)