Resolve Coverity dead_error_begin

Coverity complains about default: label in libxl_driver.c not be able
to be reached. It's by design for the code and since it's not necessary
in the code nor does it elicit any compiler/make check warnings - just
remove it rather than adding a coverity[dead_error_begin] tag.

While I'm at it, lxc_driver.c and nodeinfo.c have the same design, so I
removed the default labels and the existing coverity tags.

src/libxl/libxl_driver.c

@@ -4167,9 +4167,6 @@ libxlDomainGetNumaParameters(virDomainPtr dom,
             nodeset = NULL;
 
             break;
-
-        default:
-            break;
         }
     }
 

src/lxc/lxc_driver.c

@@ -950,11 +950,6 @@ lxcDomainGetMemoryParameters(virDomainPtr dom,
                                         VIR_TYPED_PARAM_ULLONG, val) < 0)
                 goto cleanup;
             break;
-
-        /* coverity[dead_error_begin] */
-        default:
-            break;
-            /* should not hit here */
         }
     }
 
@@ -2626,11 +2621,6 @@ lxcDomainGetBlkioParameters(virDomainPtr dom,
                                             param->value.s) < 0)
                     goto cleanup;
                 break;
-
-            /* coverity[dead_error_begin] */
-            default:
-                break;
-                /* should not hit here */
             }
         }
     } else if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
@@ -2818,11 +2808,6 @@ lxcDomainGetBlkioParameters(virDomainPtr dom,
                     goto cleanup;
                 }
                 break;
-
-            /* coverity[dead_error_begin] */
-            default:
-                break;
-                /* should not hit here */
             }
         }
     }

src/nodeinfo.c

@@ -1478,10 +1478,6 @@ nodeGetMemoryParameters(virTypedParameterPtr params ATTRIBUTE_UNUSED,
                 return -1;
 
             break;
-
-        /* coverity[dead_error_begin] */
-        default:
-            break;
         }
     }