Send GPU data to master

I'd do a couple of things differently here.  First, I'd put the paths in the agent.yml config:

```yaml
# A list of paths or names where the `lspci` command can
# be called from on Linux.  This is used to retrieve information
# for about graphics cards installed on the system in 
# `pyfarm.agent.sysinfo.graphics.graphics_cards`.  If you need 
# run the command with sudo you may also specify an entry
# like this:
#  - sudo lspci
sysinfo_command_lspci:
  - lspci
  - /bin/lspci
  - /sbin/lspci
  - /usr/sbin/lspci
  - /usr/bin/lspci
```

That way someone can add their own paths or change the way the command is called if necessary.  On a couple of systems I had handy you cannot run the command without sudo and it didn't live in the paths you're checking below either.  With the config it should be a problem for anyone in the future who may need to change it.

The second thing I'd is call the executable directly rather than using `isfile()`.  This will be more reliable and with let `$PATH` do the work first in the default case.

```python
from subprocess import CalledProcessError, check_output

gpu_names = []
for lspci_command in config["sysinfo_command_lspci"]:
    try:
        output = check_output(*lspci_command.split(" "))

    except CalledProcessError as e:
        logger.warning("Failed to call %r, will", lspci_command)
        continue

    for line in output.splitlines():
        gpu_names.append(line.split(":", 2)[2].strip())
    break

else:
    raise GPULookupError("Failed to locate the lspci command")
```