Get build:env:create to respect .gitignore files

[generalredneck]

terminus build:env:create runs git -C /home/tester/project add --force -A . which ignores .gitignore files and just adds everything. There is a --no-git-force option but then it doesn't git -C /home/tester/project push --force -q pantheon pr-1 which causes problems when rebuilding an environment. Update the script to reset the pr branch to the source commit prior to running build:env:create with the --no-git-force option.