net: call getSystemDNSConfig inside lookupWithFake to avoid nil dereference panic when running tests alone
It happens with tests that only call lookupWithFake, and before them no-one calls resolverConf.tryUpdate. running alone one of these: TestIssue8434, TestIssueNoSuchHostExists cause a nil dereference panic.
Change-Id: I3fccd96dff5b3c77b5420a7f73742acbafa80142
GitHub-Last-Rev:
7456fd16a7ff4845b4ca305d4107d29f1d6f7b3e
GitHub-Pull-Request: golang/go#56759
Reviewed-on: https://go-review.googlesource.com/c/go/+/450856
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>