service_spec: force ceph-exporter sock_dir to be unest or "/var/run/ceph/"

As discussed in https://tracker.ceph.com/issues/69475 this
setting is effectively useless as it only controls the directory
inside the container where the ceph-exporter will write out
its asok file, and has no influence over where it is on the
host where the ceph-exporter daemon is deployed. Given any
custom values for the sock_dir setting would have always
been broken, we decided to skip out on writing a proper migration
step in cephadm to deal with this, and instead just force this
field to be unset

Signed-off-by: Adam King <[email protected]>

Author: adk3798

src/python-common/ceph/deployment/service_spec.py

@@ -2868,7 +2868,7 @@ def __init__(self,
             extra_entrypoint_args=extra_entrypoint_args)
 
         self.service_type = service_type
-        self.sock_dir = sock_dir
+        self.sock_dir = None
         self.addrs = addrs
         self.port = port
         self.prio_limit = prio_limit
@@ -2880,6 +2880,11 @@ def get_port_start(self) -> List[int]:
     def validate(self) -> None:
         super(CephExporterSpec, self).validate()
 
+        if self.sock_dir and self.sock_dir != '/var/run/ceph/':
+            raise SpecValidationError(
+                'sock_dir setting is deprecated and must be either unset or set to /var/run/ceph/'
+            )
+
         if not isinstance(self.prio_limit, int):
             raise SpecValidationError(
                     f'prio_limit must be an integer. Got {type(self.prio_limit)}')