spec: abort runner on Errno::ENOMEM

ABORT_ON_CONSISTENT_BADNESS doesn't catch it if it happens during driver
setup. rather than retrying 10 times, just bail and hope that the other
test-queue nodes will have better luck

test plan:

1. see earlier patchsets how test-queue runners stopped when they hit
   those, and other runners got the rest of the specs

Change-Id: I2bdfeafd8fbf5e1404952d92548f4ae62567575e
Reviewed-on: https://gerrit.instructure.com/73546
Reviewed-by: Ethan Vizitei <evizitei@instructure.com>
Tested-by: Jenkins
Product-Review: Jon Jensen <jon@instructure.com>
QA-Review: Jon Jensen <jon@instructure.com>

spec/selenium/common.rb

@@ -66,6 +66,10 @@ shared_context "in-process server selenium tests" do
 
   def maybe_recover_from_exception(exception)
     case exception
+    when Errno::ENOMEM
+      # no sense trying anymore, give up and hope that other nodes pick up the slack
+      puts "Error: got `#{exception}`, aborting"
+      RSpec.world.wants_to_quit = true
     when EOFError, Errno::ECONNREFUSED, Net::ReadTimeout
       if $selenium_driver && !RSpec.world.wants_to_quit && exception.backtrace.grep(/selenium-webdriver/).present?
         puts "SELENIUM: webdriver is misbehaving.  Will try to re-initialize."