Upgrade helper image alpine 3.7
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What does this MR do?
Upgrade helper image to alpine 3.7 Install git-lfs from package repository
Why was this MR needed?
alpine 3.7 provides git 2.15.2 which improves git-lfs support (batch call to the lfs server when cloning submodules)
Are there points in the code the reviewer needs to double check?
Does this MR meet the acceptance criteria?
- 
Documentation created/updated  - Tests
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Added for this feature/bug  - 
All builds are passing  
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Branch has no merge conflicts with master(if you do - rebase it please)