xunit publisher was wrong with multiple types

When using multiple xunit publishers such as:

  publishers:
   - xunit:
	  types:
	   - phpunit:
		  pattern: 'junitphp.xml'
	   - cppunit:
		  pattern: 'cppunit.log'

the publisher was wrapping each framework (phpunit, cppunit in above
example) in its own <types /> which is not at all how the Jenkins plugin
does it.

Instead, this patch creates a single <types /> element and attach all
frameworks to it.

Change-Id: I6822d6355e7ba47546f6e959e3d1a160a059243b
Merge "xunit publisher was wrong with multiple types"