Add NetHttpCoverageTests to mainline presubmit

Mainline presubmit runs on older images. So we need to set:
- min_sdk_version to the minimum sdk we support otherwise
it would default to current
- enforce_default_target_sdk_version since mainline needs
all modules to target the latest sdk

Test: presubmit
Bug: 263294440
Change-Id: I20757b13ab9ab45908dae088c6cb6b0bbc51989d
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 4d3ecdf..70c5f85 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -213,6 +213,9 @@
     },
     {
       "name": "libnetworkstats_test[CaptivePortalLoginGoogle.apk+NetworkStackGoogle.apk+com.google.android.resolv.apex+com.google.android.tethering.apex]"
+    },
+    {
+      "name": "NetHttpCoverageTests[CaptivePortalLoginGoogle.apk+NetworkStackGoogle.apk+com.google.android.resolv.apex+com.google.android.tethering.apex]"
     }
   ],
   "mainline-postsubmit": [