Update variable definition inside tcar.sh.
    
    - Previously, TCAR_BASEDIR was pointing to automation scripts
      directory. This is incorrect because TCAR_BASEDIR must point to the
      root directory where The CentOS Artwork Repository was installed in
      (e.g., /usr/share/tcar). This update changes TCAR_BASEDIR value to
      hold the correct value and adds the TCAR_SCRIPT_BASEDIR variable to
      hold the root location of automation scripts.
    
    - Previously, the =TCAR_WORKDIR= translation marker expanded to
      TCAR_BASEDIR. This is incorrect because TCAR_WORKDIR and
      TCAR_BASEDIR have not the same value. This update prevents
      =TCAR_WORKDIR= from expanding to TCAR_BASEDIR value.