Do not set pid file for iscsid

Kolla Ansible runs iscsid in the foreground (-f) and
a recent change to iscsid in CentOS 8 (both Linux and Stream)
caused it to reject setting pid file in such a case.
PID file is irrelevant in this scenario so this commit
removes its parameter.

Closes-Bug: #1933033
Change-Id: Ic0c4beae0c812f3ca68a6ee5cc4daa2fee0f277d

ansible/roles/iscsi/templates/iscsid.json.j2

 {
-    "command": "iscsid -d 8 -f --pid=/run/iscsid.pid",
+    "command": "iscsid -d 8 -f",
     "config_files": []
 }

releasenotes/notes/bug-1933033-76746d127285cfe8.yaml

+---
+fixes:
+  - |
+    Fixes ``iscsid`` failing in current CentOS 8 based images due to
+    pid file being needlessly set.
+    `LP#1933033 <https://launchpad.net/bugs/1933033>`__