Add KCAS_ERR_CORE_IN_ACTIVE_STATE error code.

New error code will allow to properly handle issues caused by wrong
usage of `remove inactive core` command.
It will also allow to print meaningful error messages.

Signed-off-by: Slawomir Jankowski <slawomir.jankowski@intel.com>

modules/cas_cache/utils/cas_err.h

@@ -65,6 +65,7 @@ struct {
 	{ KCAS_ERR_A_PART,			EINVAL	},
 	{ KCAS_ERR_REMOVED_DIRTY,		EIO	},
 	{ KCAS_ERR_STOPPED_DIRTY,		EIO	},
+	{ KCAS_ERR_CORE_IN_ACTIVE_STATE,	ENODEV	},
 };
 
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