Fix selenium layer count check.
Fix selenium layer count check.

Was hard coded to 17, but sometimes the mapbook changes.  Allow to
pass when > 10, so this isn't so fragile.  The main goal is to see
if IE11 works at all.  More detailed tests can follow if needed.

ref: #391

geomoose/gm3,geomoose/gm3,geomoose/gm3