(2.8) webadmin: fix regression in alarm deletion filter

Patch 6344 introduced a regression in the webadmin alarms
management which prohibits the deletion of entries.

See http://rb.dcache.org/r/6344.

which forced a range limit on the number of
entries returned by a query.  JDO does not allow
a range to be specified this way on a deletion query,
but this case was overlooked.

This patch remedies the oversight.

Testing:

Deployed with patch; successfully deleted checked entries from table.

Target: 2.9
Request: 2.8
Request: 2.7
Request: 2.6
Require-book: no
Require-notes: yes
Acked-by: Karsten
Acked-by: Paul
Committed: 37407965bbcfe197fd9eaaba894d39cfcb1113d1

RELEASE NOTES:  Fixes a regression in the webadmin alarms
page preventing the deletion of entries from the alarm
table.