Sets hpctixfile to be unique for every postgrest process that is run. Previously, this was based on the test name, but issues arise when two postgrest processes are run under the same test, which generates two files where one gets overwritten by the other. Consequently, coverage data used to get lost, which is now fixed with this commit. Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>