CLDSRV-992: Build the uploadPartCopy fixtures once per suite, not per test

Both `uploadPartCopy` describes in the PartNumber tests rebuild a large MPU
fixture in a beforeEach, although all four of their tests only issue a
GetObject. Each rebuild moves roughly 200 MB: completeMPU uploads ten 5 MB
parts one at a time with async.eachSeries, createMPUAndPutTwoParts copies that
50 MB object and then puts a 50 MB body, and the overwrite variant adds a 5 MB
part and a second 50 MB UploadPartCopy. Doing that twice per describe, once for
each read-only test, is what pushes the hook past the 40 s mocha timeout on the
s3c backend.

Move the setup to `before` and the DeleteObject cleanup to `after`. The fixture
is identical for both tests in each describe, and the enclosing describe creates
the bucket in its own `before` and drops it in `after`, so the fixture safely
outlives the individual tests. Halves the data moved by these two describes and
removes the redundant rebuild, rather than raising the timeout.

Clears the timeout half of CLDSRV-992 row F8 (run 33647777908): the "before
each" hook for "should retrieve a part that overwrote another part originally
copied from an MPU". The same row's ServiceUnavailable on "should get the body
of part 8 when ordered MPU" is a separate transient and is not addressed here.

Issue: CLDSRV-992

Author: anurag4DSB

tests/functional/aws-node-sdk/test/object/get.js

@@ -923,7 +923,7 @@ describe('GET object', () => {
                 const partOneBody = Buffer.concat(bufs, partOneSize);
                 const partTwoBody = Buffer.alloc(partSize, 4);
 
-                beforeEach(done => async.waterfall([
+                before(done => async.waterfall([
                     next => completeMPU(orderedPartNumbers, next),
                     next => createMPUAndPutTwoParts(partTwoBody, next),
                     (uploadId, ETags, next) =>
@@ -946,7 +946,7 @@ describe('GET object', () => {
                         }, next),
                 ], done));
 
-                afterEach(done => s3.deleteObject({
+                after(done => s3.deleteObject({
                     Bucket: bucketName,
                     Key: copyPartKey,
                 }, done));
@@ -968,7 +968,7 @@ describe('GET object', () => {
                     Buffer.alloc(partSize, n));
                 const partTwoBody = Buffer.concat(bufs, partTwoSize);
 
-                beforeEach(done => async.waterfall([
+                before(done => async.waterfall([
                     next => completeMPU(orderedPartNumbers, next),
                     next => createMPUAndPutTwoParts(partTwoBody, next),
                     /* eslint-disable no-param-reassign */
@@ -1019,7 +1019,7 @@ describe('GET object', () => {
                         }, next),
                 ], done));
 
-                afterEach(done => s3.deleteObject({
+                after(done => s3.deleteObject({
                     Bucket: bucketName,
                     Key: copyPartKey,
                 }, done));