Removed more AMD-specific features from cpu64-rhel* models

We found few more AMD-specific features in cpu64-rhel* models that
made it impossible to start qemu guest on Intel host (with this
setting) even though qemu itself starts correctly with them.
This impacts one test, thus the fix in tests/cputestdata/.

src/cpu/cpu_map.xml

@@ -347,7 +347,6 @@
     </model>
 
     <model name='cpu64-rhel6'>
-      <feature name='abm'/>
       <feature name='apic'/>
       <feature name='clflush'/>
       <feature name='cmov'/>
@@ -373,7 +372,6 @@
       <feature name='sse'/>
       <feature name='sse2'/>
       <feature name='pni'/>
-      <feature name='sse4a'/>
       <feature name='syscall'/>
       <feature name='tsc'/>
     </model>

tests/cputestdata/x86-baseline-no-vendor-result.xml

 <cpu mode='custom' match='exact'>
-  <model fallback='allow'>kvm64</model>
-  <feature policy='require' name='lahf_lm'/>
+  <model fallback='allow'>cpu64-rhel6</model>
 </cpu>