Raise ConfigFilesNotFoundError if CONF.api_paste_config not found

Otherwise it shows an incomprehensible message
"'NoneType' object has no attribute 'startswith'."

Change-Id: I5d87c4ceac69b26730d63727a2ec3701ccc9cecb
Closes-bug: 1236182
Prevent L3 agent looping calls from hanging

This patch adopts several measures to prevent _sync_routers_task
and _rpc_loop from hanging because of subprocess.Popen.communicate
not returning.

1) Perform a sleep everytime a command is completed, similarly to
what is done in openstack.common.processutils.execute
2) Disable by default GARP, as kernel crashes caused by arping
have been observed
3) Prevent a non-critical keyerror in _router_removed from triggering
again a full sync, which might put the system under significant load.

This patch also adds debug log statements aimed at improving the
ability of debugging similar failures.

Change-Id: I003316bce0f38b7d2ea7d563b5a0a58676834398
Partial-Bug: 1224001
Merge "Prevent L3 agent looping calls from hanging"
Utilizes assertNotIn

Using assertTrue and the 'not in' operator to test
if an element is in a sequence is too python2.4.
Our unit testing framework supports assertNotIn
which was created for these types of tests.

Fixes bug #1230028

Change-Id: Ibaf6c73c514b9ad27f8f37eb3f1043e31dbfdcc1
Merge "Raise ConfigFilesNotFoundError if CONF.api_paste_config not found"
Imported Translations from Transifex

Change-Id: I7ff99a23bc300d05d06ffa2d0ccc9f5742216155
Merge "Utilizes assertNotIn"
Merge "Imported Translations from Transifex"