Better error catching for app role check

Catch when vault is sealed.
Retries are only necessary for the internal server error (which
indicates a DB failure).

Change-Id: I5aae05dd2902094874500022ac18661a24f5726d
Related-Bug: #1866150

src/lib/charm/vault.py

@@ -236,6 +236,8 @@ def get_client(url=None):
 
 @tenacity.retry(wait=tenacity.wait_exponential(multiplier=1, max=60),
                 stop=tenacity.stop_after_attempt(8),
+                retry=tenacity.retry_if_exception_type(
+                    hvac.exceptions.InternalServerError),
                 reraise=True)
 def get_local_client():
     """Provide a client for talking to the vault api

src/reactive/vault_handlers.py

@@ -727,7 +727,8 @@ def client_approle_authorized():
         vault.get_local_client()
         return True
     except (vault.hvac.exceptions.InternalServerError,
-            vault.VaultNotReady):
+            vault.VaultNotReady,
+            vault.hvac.exceptions.VaultDown):
         log("InternalServerError: Unable to athorize approle. "
             "This may indicate failure to communicate with the database ",
             "WARNING")