Refactor RAND_set_entropy_source #798

Job	Run time
run-checker (no-cmp)	4m 5s
run-checker (no-cms)	4m 12s
run-checker (no-ct)	4m 6s
run-checker (no-dtls)	4m 12s
run-checker (no-ec)	3m 36s
run-checker (no-ec2m)	3m 57s
run-checker (no-legacy)	4m 13s
run-checker (no-sock)	4m 13s
run-checker (no-srp)	4m 12s
run-checker (no-srtp)	4m 13s
run-checker (enable-ssl-trace)	4m 16s
run-checker (no-tests)	1m 52s
run-checker (no-threads)	4m 12s
run-checker (no-tls)	4m 10s
run-checker (no-tls1_2)	4m 10s
run-checker (no-tls1_3)	4m 19s
run-checker (enable-trace enable-fips)	4m 51s
run-checker (enable-ntls)	4m 10s
run-checker (no-ts)	4m 6s
run-checker (no-ui)	4m 12s
	1h 21m 17s

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