pgsql: Give a proper error message if initdb password file is empty.

Give a proper error message if initdb password file is empty.

Used to say just "could not read password from file "...": Success", which
isn't very informative.

Mats Erik Andersson. Backpatch to all supported versions.

Branch
------
REL9_2_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/2b53d583de96e82d98b1f87c9fbc9f60aa292c9e

Modified Files
--------------
src/bin/initdb/initdb.c |    8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)