Fix host metadata kernel information (#2104)

Author: andrewlock

tracer/src/Datadog.Trace/PlatformHelpers/HostMetadata.cs

@@ -114,6 +114,7 @@ private static void TryGetKernelInformation(out string kernel, out string kernel
                     var fullVersion = File.ReadAllText("/proc/version");
 
                     ParseKernel(fullVersion, out kernel, out kernelRelease, out kernelVersion);
+                    return;
                 }
             }
             catch

tracer/test/Datadog.Trace.Tests/PlatformHelpers/HostMetadataTests.cs

@@ -50,6 +50,17 @@ public void CanParseMalformedKernels(
             version.Should().Be(expectedVersion);
         }
 
+        [Fact]
+        public void CanRetrieveKernelInfo()
+        {
+            if (FrameworkDescription.Instance.OSPlatform == OSPlatform.Linux)
+            {
+                HostMetadata.Instance.KernelName.Should().NotBeNullOrEmpty();
+                HostMetadata.Instance.KernelRelease.Should().NotBeNullOrEmpty();
+                HostMetadata.Instance.KernelVersion.Should().NotBeNullOrEmpty();
+            }
+        }
+
         public static class TestData
         {
             /// <summary>