Werk #15293: mk_oracle: fix custom sql sid matching

Configuration variable $SQLS_SIDS can be used to define a comma seperated list of sids for which the custom sql is executed.

Before this werk the custom sql was executed if the sid was a substring of one of the elements of the list in $SQLS_SIDS.

Now custom sql is only executed if the sid is equal to the whole element provided in $SQLS_SIDS.

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