pgsql: Fix inappropriate error messages for Hot Standby misconfiguratio

Fix inappropriate error messages for Hot Standby misconfiguration errors.

Give the correct name of the GUC parameter being complained of.
Also, emit a more suitable SQLSTATE (INVALID_PARAMETER_VALUE,
not the default INTERNAL_ERROR).

Gurjeet Singh, errcode adjustment by me

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/987277f402a31ba91ea647d115785e5a4f7850fa

Modified Files
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src/backend/access/transam/xlog.c |    9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)