pgsql: Switch pg_basebackup commands in Postgres.pm to use --nosync

Switch pg_basebackup commands in Postgres.pm to use --nosync

On slow machines, this greatly reduces the I/O pressure induced by the
tests.

From: Michael Paquier 

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/728a3e73e96173bb0b0b2afc0da061991f9e3d5d

Modified Files
--------------
src/test/perl/PostgresNode.pm | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)