Fix typo for Czech (cs) L10N.

Otherwise get e.g.:
java.lang.IllegalArgumentException: java.lang.NullPointerException
	at hudson.model.ItemGroupMixIn.createProject(ItemGroupMixIn.java:253)
	at hudson.model.ItemGroupMixIn.createTopLevelItem(ItemGroupMixIn.java:175)
	at jenkins.model.Jenkins.doCreateItem(Jenkins.java:2827)
	at jenkins.model.Jenkins.doCreateItem(Jenkins.java:308)
	at …
Caused by: java.lang.NullPointerException
	at hudson.model.ItemGroupMixIn.createProject(ItemGroupMixIn.java:251)
	... 65 more

Throw Failure, which FormException would just delegate to when we are not coming from a regular form’s Apply button, as in this case.

https://jenkins.ci.cloudbees.com/job/core/job/jenkins_main_trunk/1369/testReport/junit/hudson.model/AsynchPeopleTest/display/
org.junit.ComparisonFailure: expected:<[display: none;]> but was:<[]>
	at org.junit.Assert.assertEquals(Assert.java:115)
	at org.junit.Assert.assertEquals(Assert.java:144)
	at hudson.model.AsynchPeopleTest.display(AsynchPeopleTest.java:44)
was presumably a race condition.
Could reproduce by adding a Thread.sleep into AsynchPeople.compute.
This patch (with waitForBackgroundJavaScript) avoids that error;
but causes the assertNotNull at the end to fail, for reasons TBD.

[FIXED JENKINS-20143] Pass full list of all possible jobs to ViewJobFilter when recurse option is set

The implementation of the method is rather hard to follow so this certainly needs to be tested!

Sources are UTF-8 so might as well use the raw character when specifying something that will be a part of output.

[FIXED JENKINS-20071] Upgrade bundled versions of credentials and ssh-slaves so we can assume <c:select/> available