Fixing Neutron Subnet Details help text

Removing the '&lt;' and '&gt;' tags which were wrongly displayed in
the help text of the Subnet Details dialog for Neutron Networks /
Subnet create.

Closes-Bug: #1311820
Change-Id: I9e730a2d90a6174634c3233230e48e63549e1b9c
Merge "Fixing Neutron Subnet Details help text"