[#2387] Fix final commit in pqm merge.

Problem
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PQM was pushing changes to the default location... not requesting an explicit locations.

On server PQM, the repo has reach a state where default push were done on 3 locations  

Changes
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Update to only push on master.


How to test
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reviewers: @alibotean 

we need to use it on server as other repo have a single target for push... and I don't know how  to configure a git repo so that by default to push to 3 branches.

thanks!