Upload coverage report from outside of test container.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

scripts/test/unit-with-coverage

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+for pkg in $(go list ./... | grep -v /vendor/); do
+    ./scripts/test/unit \
+        -cover \
+        -coverprofile=profile.out \
+        -covermode=atomic \
+        ${pkg}
+    
+    if test -f profile.out; then
+        cat profile.out >> coverage.txt
+        rm profile.out
+    fi
+done