RFR: 8254602: compiler/debug/TestStressCM.java failed with "RuntimeException: got the same optimization stats for different seeds: expected 45"

[Roberto Castañeda Lozano]

Remove test assertion checking that different random seeds lead to different code motion decisions. This was the case
for the specific pair of random seeds, IR fed to code motion, and target platforms tested originally; but does not need
to hold in general. Remove similar test assertion in IGVN randomization test case. Re-enable the test case.

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Commit messages:
 - 8254602: compiler/debug/TestStressCM.java failed with "RuntimeException: got the same optimization stats for different seeds: expected 45"

Changes: https://git.openjdk.java.net/jdk/pull/626/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=626&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254602
  Stats: 14 lines in 3 files changed: 0 ins; 9 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/626.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/626/head:pull/626

PR: https://git.openjdk.java.net/jdk/pull/626