Use calico_pool_blocksize from cluster when existing

The blockSize attribute from Calico IPPool resources cannot be changed
once set [1]. Consequently, we use the one currently defined when
configuring the existing IPPool, avoiding upgrade errors by trying to
change it.

In particular, this can be useful when calico_pool_blocksize default
changes in kubespray, which would otherwise force users to add an
explicit setting to their inventories.

[1]: https://docs.tigera.io/calico/latest/reference/resources/ippool#spec

roles/network_plugin/calico/tasks/install.yml

@@ -232,10 +232,17 @@
           }
 
     - name: Calico | Process calico network pool
-      set_fact:
-        _calico_pool: "{{ _calico_pool_cmd.stdout | from_json | combine(_calico_pool, recursive=True) }}"
       when:
         - _calico_pool_cmd is success
+      block:
+      - name: Calico | Get current calico network pool blocksize
+        set_fact:
+          _calico_blocksize:
+            spec:
+              blockSize: "{{ (_calico_pool_cmd.stdout | from_json).spec.blockSize }}"
+      - name: Calico | Merge calico network pool
+        set_fact:
+          _calico_pool: "{{ _calico_pool_cmd.stdout | from_json | combine(_calico_pool, _calico_blocksize, recursive=True) }}"
 
     - name: Calico | Configure calico network pool
       command:
@@ -273,10 +280,17 @@
           }
 
     - name: Calico | Process calico ipv6 network pool
-      set_fact:
-        _calico_pool_ipv6: "{{ _calico_pool_ipv6_cmd.stdout | from_json | combine(_calico_pool_ipv6, recursive=True) }}"
       when:
         - _calico_pool_ipv6_cmd is success
+      block:
+      - name: Calico | Get current calico ipv6 network pool blocksize
+        set_fact:
+          _calico_blocksize_ipv6:
+            spec:
+              blockSize: "{{ (_calico_pool_ipv6_cmd.stdout | from_json).spec.blockSize }}"
+      - name: Calico | Merge calico ipv6 network pool
+        set_fact:
+          _calico_pool_ipv6: "{{ _calico_pool_ipv6_cmd.stdout | from_json | combine(_calico_pool_ipv6, _calico_blocksize_ipv6, recursive=True) }}"
 
     - name: Calico | Configure calico ipv6 network pool
       command: