webadmin: iSCSI login button arrow not properly aligned

Login button of the iSCSI storage domain dialog was misplaced after introducing
the http://gerrit.ovirt.org/#/c/32521/

This patch fixes it.

Change-Id: I609b4cb800e75a76ffacfe9a515bf495ccf281c2
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>