AIDEGen: Skip error message of git command to get user's LDAP

Do not show error message even the git config command can't get user's
email.

Bug: 128444947
Test: 1. vi ~/.gitconfig
      2. remove whole content of [user]
      3. m aidegen
      4. aidegen-dev framework
      5. No error message about subprocess.CalledProcessError.

Change-Id: I63faf4ab98d9a4ccd0f36190218dbbbe30849c68
1 file changed