PEL: Prevent deletion if it's associated with HWIsolation

- This ensures that PELs linked to HWIsolation records are protected
from accidental deletion.
- Shows error message of "Call failed: The service is temporarily
unavailable.", when attempting to delete such a PEL individually.
- If trying to Delete all, will skip such PELs without showing any
message.

Tested:
Sample output:
```bash
$ busctl call xyz.openbmc_project.Logging /xyz/openbmc_project/
logging xyz.openbmc_project.Collection.DeleteAll DeleteAll

$ busctl call xyz.openbmc_project.Logging /xyz/openbmc_project/
logging/entry/2 xyz.openbmc_project.Object.Delete Delete
Call failed: The service is temporarily unavailable.

```
Change-Id: I2d28de91bbb0fbc2a991e3d5e5631814d41fe044
Signed-off-by: Harsh Agarwal <Harsh.Agarwal@ibm.com>
diff --git a/log_manager.hpp b/log_manager.hpp
index cc42d8a..436f572 100644
--- a/log_manager.hpp
+++ b/log_manager.hpp
@@ -116,20 +116,7 @@
      *
      *  @return size_t - count of erased entries
      */
-    size_t eraseAll()
-    {
-        size_t entriesSize = entries.size();
-        auto iter = entries.begin();
-        while (iter != entries.end())
-        {
-            auto e = iter->first;
-            ++iter;
-            erase(e);
-        }
-        entryId = 0;
-
-        return entriesSize;
-    }
+    size_t eraseAll();
 
     /** @brief Returns the count of high severity errors
      *