Fix commitFromGit -> gitCommit in release/build-release.sh

This caused Jenkins break on e2e-test because the version of server and
client did not match exactly, as the server was built without the
version ldflags.

Tested:
- Ran "release/build-release.sh ${instance_name}" and confirmed that
  output/release/master-release/src/saltbase/pillar/common.sls has the
  git version under version.gitCommit no longer version.commitFromGit.

Fixes: b777eb19e25240520b5122de299d9ee270c76017
Merge pull request #1062 from filbranden/versioning_fixes3

Fix commitFromGit -> gitCommit in release/build-release.sh