Log dnsmasq host file generation

We've been seeing things that appear to be races between the hosts
files being written out for dnsmasq and dhcp requests coming in.  We
will get occasional errors from dnsmasq saying "no address available",
"duplicate IP address" but by the time you look, the corresponding
host file has long since been replaced.

If we had some debugging like this, we could at least correlate what
neutron thought dnsmasq knew at the time the requests were coming in.

We store the filename to avoid multiple lookups, and also
s/name/filename/ to avoid ambiguity and be more consistent with the
rest of the code.

Closes-Bug: #1294892
Change-Id: Ifa92ca71419ce0155b28d2015eff9e82557a0825
Remove extra space in help string

Extra spaces make the openstack-manuals tests fail with a niceness
error. This patch removes an extra space at the end of a help string.

Change-Id: I29bab90ea5a6f648c4539c7cd20cd9b2b63055c2
Merge "Log dnsmasq host file generation"
Merge "Remove extra space in help string"