RFR: 8374082: net_util.c should use logical && when setting IPv6_available

[Jaikiran Pai]

Can I please get a review of this change which replaces the use of `&` with `&&` in net_util.c?

As noted in https://bugs.openjdk.org/browse/JDK-8374082, the use of bitwise operator appears to be an oversight in that code.

tier1, tier2 testing passed without any issues after this change.

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Commit messages:
 - use && instead of &

Changes: https://git.openjdk.org/jdk/pull/28918/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28918&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374082
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28918.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28918/head:pull/28918

PR: https://git.openjdk.org/jdk/pull/28918