Backporting the 301 redirect fix to v3 branch

[jeffposnick]

R: @philipwalton

Fixes #1677

This takes the v4 change from #1678 and backports it to the v3 branch.

After doing some git digging, the change that introduced the issue turned out to be https://github.com/GoogleChrome/workbox/pull/828/files#diff-37d7dc9fcc2f99bebe79d4b453e132fe, i.e. it looks inadvertant, so I can't think of a reason why we wouldn't want this code to be in v3.x.

[philipwalton]

LGTM

[workbox-pr-bot]

PR-Bot Size Plugin

Changed File Sizes

File	Before	After	Change	GZipped
packages/workbox-precaching/build/workbox-precaching.prod.js	5.81 KB	5.80 KB	-0%	2.24 KB

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All File Sizes

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File	Before	After	Change	GZipped
packages/workbox-background-sync/build/workbox-background-sync.prod.js	3.51 KB	3.51 KB	0%	1.45 KB
packages/workbox-broadcast-cache-update/build/workbox-broadcast-cache-update.prod.js	1.12 KB	1.12 KB	0%	585 B
packages/workbox-build/build/_types.js	41 B	41 B	0%	61 B
packages/workbox-build/build/index.js	4.02 KB	4.02 KB	0%	1.57 KB
packages/workbox-cache-expiration/build/workbox-cache-expiration.prod.js	3.88 KB	3.88 KB	0%	1.37 KB
packages/workbox-cacheable-response/build/workbox-cacheable-response.prod.js	587 B	587 B	0%	347 B
packages/workbox-cli/build/app.js	6.76 KB	6.76 KB	0%	2.27 KB
packages/workbox-cli/build/bin.js	2.32 KB	2.32 KB	0%	1.03 KB
packages/workbox-core/build/workbox-core.prod.js	7.47 KB	7.47 KB	0%	2.90 KB
packages/workbox-google-analytics/build/workbox-google-analytics.prod.js	2.12 KB	2.12 KB	0%	1.03 KB
packages/workbox-navigation-preload/build/workbox-navigation-preload.prod.js	660 B	660 B	0%	319 B
packages/workbox-precaching/build/workbox-precaching.prod.js	5.81 KB	5.80 KB	-0%	2.24 KB
packages/workbox-range-requests/build/workbox-range-requests.prod.js	1.63 KB	1.63 KB	0%	797 B
packages/workbox-routing/build/workbox-routing.prod.js	2.87 KB	2.87 KB	0%	1.31 KB
packages/workbox-strategies/build/workbox-strategies.prod.js	5.09 KB	5.09 KB	0%	1.24 KB
packages/workbox-streams/build/workbox-streams.prod.js	1.57 KB	1.57 KB	0%	740 B
packages/workbox-sw/build/workbox-sw.js	1.50 KB	1.50 KB	0%	811 B
packages/workbox-webpack-plugin/build/generate-sw.js	8.04 KB	8.04 KB	0%	2.57 KB
packages/workbox-webpack-plugin/build/index.js	742 B	742 B	0%	470 B
packages/workbox-webpack-plugin/build/inject-manifest.js	10.30 KB	10.30 KB	0%	3.23 KB

Workbox Aggregate Size Plugin

9.97KB gzip'ed (66% of limit)
26.56KB uncompressed