Revert "Use --unset to remove the credentials store from the git config"
running :

    git config --local foo.bar qix
    git config --local --unset foo.bar
    git config --local foo.bar qix

result in (unexpected) dublicate [foo] section. Looks like a git bug.

This reverts commit 0390acb4c5af51cbc62359122d6719a95dfb452c.
[JENKINS-21016] fix git credentials so that password is included in file and correct syntax of store command
[JENKINS-21016] do not actually need to replace path with forward slashes, so revert.  More importantly need the credentials on a single line so that the git command can read successfully
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/main/java/org/jenkinsci/plugins/gitclient/CliGitAPIImpl.java