webadmin: add PatternFly style fix to DiskItemView

DisksAllocationItemView ->
added "avw_contentWidget_pfly_fix" style to
content widget (needed for disk alias textbox).

Before-Screenshot: http://i.imgur.com/Gy5VluW.jpg
After-Screenshot: http://i.imgur.com/J5TypMQ.jpg

Change-Id: Ief0490da44b815a32d529bdb676820b29e71e8ff
Signed-off-by: Daniel Erez <derez@redhat.com>