Do not call session_start() on CLI processes

This is a refinement of the idea in civicrm/civicrm-wordpress#135 to address other CLI use-cases.

Before
-------

If I have a `wpmaster` site on on `bknix-max` (php73), and if I run `cv upgrade:db -vv`, then there are several warnings like this:

After
-----

It doesn't try to start session in CLI (where sessions don't make sense).

Signed-off-by: Kevin Cristiano <kcristiano@kcristiano.com>

civicrm.php

@@ -367,7 +367,7 @@ public function setup_instance() {
      * There is no session handling in WP - hence we start it for CiviCRM pages
      * except when running via WP-CLI which does not require sessions.
      */
-    if ( empty( $session_id ) && ! ( defined( 'WP_CLI' ) && WP_CLI ) ) {
+    if ( empty( $session_id ) && ! ( defined( 'WP_CLI' ) && WP_CLI ) && ( PHP_SAPI !== 'cli' ) ) {
       session_start();
     }