Adjust tests with dedicated ssl certificate to fetch it from the test directory #643

Job	Run time
Build	7s
Test (windows, head, 16.0-1-windows-x64, 16)	2m 49s
Test (windows, 2.5, 9.4.26-1-windows-x64, 9.4)	7m 2s
Test (windows, mswin, 16.0-1-windows-x64, 16)	1m 34s
Test (ubuntu, head, 16)	1m 3s
Test (ubuntu, 3.2, 12)	1m 5s
Test (ubuntu, 20.04, 2.5, 9.3)	1m 27s
Test (ubuntu, truffleruby, 13)	1m 50s
Test (ubuntu, truffleruby-head, 16)	1m 48s
Test (macos, head, 16.0-1-osx, 16)	6h 0m 15s
	6h 19m 0s

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