TT#105151 Reverse check to ensure that grub config does *not* contain net.ifnames=0

Same as 930b1c89fc without the extra code
commited by mistake.

Change-Id: I5d16ba3025949435b599583cdf2ff72630af313d

templates/830_network-interfaces-legacy.yaml.tt2

@@ -6,7 +6,7 @@ file:
     owner: root
     group: root
     filetype: file
-    contains: ['/^GRUB_CMDLINE_LINUX_DEFAULT=".*net.ifnames=0.*"/']
+    contains: ['!/^GRUB_CMDLINE_LINUX_DEFAULT=".*net.ifnames=0.*"/']
 
 command: