Use master branch instead of dev to git clone adoptOpenJDK openjdk repo

[sophia-guo]

Use master branch instead of dev to git clone adoptOpenJDK openjdk repo
as master has been updated as the default branch.
Also use shallow clone to save clone time.

Signed-off-by: Sophia Guo [email protected]

[sophia-guo]

When it's done, we can check #267 in #345

[karianna]

@sophia-guo Just to be clear - this is so you can compare the AdoptOpenJDK binary (built on dev) vs the 'pure' OpenJDK binary cloned from mercurial?

dev contains extra patches that we maintain over and above master...

[sophia-guo]

@karianna we git clone from adoptopenjdk openjdk8u repo to get latest openjdk test materials, which guarantee we can always get newest test source code and newest test fixes.
Patches for build binary are not necessary for test build. Besides seems dev is not sync with mercurial, some tests are stale in dev branch.

[karianna]

@sophia-guo We should fix dev being stale in that case as that's the branch the binaries are built from that we should be testing. I've opened adoptium/temurin-build#269

[sophia-guo]

@karianna agreed that dev branch should be in sync with openjdk mercurial especially in openjdk10 binary build will also build test image.

For regression tests we grab tests and run tests against any supported sdk binary. Supposing master will always be a pure and in sync branch with openjdk mercurial and is the right branch to clone.