fix indentation of multiline log.exception() invocations

Commit f107e39989 ("Switch to more traditional logging structure",
2019-06-17) replaced "logging.exception" with "log.exception", effectively
shifting the argument lists 4 characters to the left. The second and
further lines of multiline invocations were not accordingly unindented,
however, which ended up setting a suboptimal precedent as well. Unindent
those lines now.

Reported-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>

virtManager/hoststorage.py

@@ -427,8 +427,7 @@ class vmmHostStorage(vmmGObjectUI):
                     if not namestr:
                         namestr = None
             except Exception:  # pragma: no cover
-                log.exception("Failed to determine if storage volume in "
-                                  "use.")
+                log.exception("Failed to determine if storage volume in use.")
 
             sensitive = True
             if self._vol_sensitive_cb: