webadmin: Fixing validation of Auth Ssh Port

The field's validation was set but without using the getIsValid as part of the
general tab validation. Clicking OK forwarded the user to PM page instead of
failing the operation.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=987910
Change-Id: Ie5bc99cfeaebd2c76a09ac2255557051626acef2
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>