RFR: 8279317: compiler/jvmci/compilerToVM/DisassembleCodeBlobTest.java assumes immutable code

[Dean Long]

This test was failing in loom because of nmethod entry barriers, but there are other reasons why it shouldn't assume immutable code, such as embedded oops and NativeJump::patch_verified_entry().

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Commit messages:
 - check dissasembly layout rather than checking for immutable code

Changes: https://git.openjdk.java.net/jdk/pull/7781/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7781&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279317
  Stats: 31 lines in 1 file changed: 19 ins; 0 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7781.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7781/head:pull/7781

PR: https://git.openjdk.java.net/jdk/pull/7781