[JJBB] increase shallow clone and tweak jjbb setup

[v1v]

What

Tune the JJBB with our best practices and fix the git symmetric issues I've seen

[2021-06-14T05:39:42.766Z] + git diff --name-only 69a5fc02acbc7d5c78ce881a0a34168aeb10d259...3af801ce95d223e247d3619950bd8d0f11d2f4b4
[2021-06-14T05:39:42.767Z] fatal: Invalid symmetric difference expression 69a5fc02acbc7d5c78ce881a0a34168aeb10d259...3af801ce95d223e247d3619950bd8d0f11d2f4b4

Already solved in the past in some other projects -> elastic/beats#21409

[v1v]

See https://github.com/elastic/apm-pipeline-library/blob/5b3ac774714e8355aab8dbb85a7558de1f407e88/.ci/jobs/apm-test-pipeline-mbp.yml#L17-L18

[apmmachine]

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Build stats

• Build Cause: Pull request #1335 opened

• Start Time: 2021-06-14T11:54:15.185+0000

• Duration: 49 min 30 sec

• Commit: 4a1d9ad

Test stats 🧪

Test	Results
Failed	0
Passed	19450
Skipped	101
Total	19551

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