Extend hardware manager with data needed for inspector

* Added NetworkInterface.ip4_address
* Added HardwareManager.get_bmc_address()
* Added Memory.physical_mb

  This is total memory as reported by dmidecode, and yes,
  it's different from total, as it includes kernel reserved space.

* Added CPU.architecture

  As a side effect, get_cpus was switched to lscpu.
  Also fixes problem when get_cpus reported the current frequency
  instead of maximum one.

Change-Id: I4080d4d551eb0bb995a94ef9a300351910c09fb9

ironic_python_agent/utils.py

@@ -64,6 +64,14 @@ def execute(*cmd, **kwargs):
     return result
 
 
+def try_execute(*cmd, **kwargs):
+    """The same as execute but returns None on error."""
+    try:
+        return execute(*cmd, **kwargs)
+    except (processutils.ProcessExecutionError, OSError) as e:
+        LOG.debug('Command failed: %s', e)
+
+
 def _read_params_from_file(filepath):
     """Extract key=value pairs from a file.