NetworkPkg/HttpDxe: use error handler epilogue in TlsConfigCertificate()
    
    Introduce a FreeCACert label near the end of the function, so that we can
    keep the FreePool(CACert) statement centralized for error and success
    exits.
    
    Cc: Jiaxin Wu <jiaxin.wu@intel.com>
    Cc: Siyuan Fu <siyuan.fu@intel.com>
    Contributed-under: TianoCore Contribution Agreement 1.1
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>
    Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
    Reviewed-by: Jiaxin Wu <jiaxin.wu@intel.com>