avoid hard coded NIC names from network_DisableInterface test

client/site_tests/network_DisableInterface/network_DisableInterface.py

 import logging, re, utils
 from autotest_lib.client.bin import test
 from autotest_lib.client.common_lib import error
 
 class network_DisableInterface(test.test):
     version = 1
 
+
     def run_once(self, iface_name='wlan0'):
-        forced_up = False
 
         # use the right interface configuration utility
         self._ifconfig = 'ifconfig'
         if iface_name.startswith('hci'):
             self._ifconfig = 'hciconfig'
+            utils.system('%s %s up' % (self._ifconfig, iface_name))
+
+        # Allow 'all' keyword  - builds a list to test
+        if iface_name == 'all':
+            ifaces = utils.system_output('ls /sys/class/net/')
+            for nic in ifaces.split():
+                if nic != 'lo' and not nic.startswith('sit'):
+                    self.test_one_nic(nic)
+        else:
+            self.test_one_nic(iface_name)
+
+
+    def test_one_nic(self, iface_name='wlan0'):
+
+        forced_up=False
 
         # bring up the interface if its not already up
         if not self.is_iface_up(iface_name):
             utils.system('%s %s up' % (self._ifconfig, iface_name))
             if not self.is_iface_up(iface_name):
-                raise error.TestFail('interface failed to come up')
+                raise error.TestFail('%s failed to come up' % iface_name)
             forced_up = True
 
         # bring interface down
         utils.system('%s %s down' % (self._ifconfig, iface_name))
         if self.is_iface_up(iface_name):
-            raise error.TestFail('interface failed to go down')
+            raise error.TestFail('%s failed to go down' % iface_name)
 
         # if initial interface state was down, don't bring it back up
         if forced_up:
             return
 
         # bring interface back up
         utils.system('%s %s up' % (self._ifconfig, iface_name))
         if not self.is_iface_up(iface_name):
-            raise error.TestFail('interface failed to come up')
+            raise error.TestFail('%s failed to come back up' % iface_name)
 
 
     def is_iface_up(self, name):
         try:
             out = utils.system_output('%s %s' % (self._ifconfig, name))
         except error.CmdError, e:
             logging.info(e)
-            raise error.TestNAError('test interface not found')
+            raise error.TestNAError('"ifconfig %s" gave error %d' % (name,out) )
 
         match = re.search('UP', out, re.S)
         return match