improve GCE create_node, make sure ex_get_disktype function will not fail

[mgogoulos]

create_node supports passing ex_disk_type as either str or GCEDiskType. If you pass an str, or if you don't pass anything -most usual case I believe- it gets an str value of 'pd-standard' since it is a kwarg, then the function will fail because self.ex_get_disktype is called without the location, and line
request = '/zones/%s/diskTypes/%s' % (zone.name, name)

will break with a 'NoneType' object has no attribute 'name'

This can easily be fixed with this commit (also applies to ex_create_multiple_nodes).

Then nodes with ssh key deployed are easily created:

from libcloud.compute.providers import get_driver; from libcloud.compute.types import Provider; driver = get_driver('gce')
conn = driver('email', 'key', project='project')
node = conn.create_node(
                name=machine_name, # str
                image=image, # NodeImage
                size=size, # NodeSize
                location=location, # NodeLocation
                ex_metadata=metadata # {'sshKeys': 'user:%s' % public_ssh_rsa_key}
            )

[erjohnso]

Looks good @mgogoulos, but tests are not passing. Do you think you can take a look at travis and get them fixed up? For example, https://travis-ci.org/apache/libcloud/jobs/50234015#L5396.

[mgogoulos]

I've added the missing fixture for this, it should complete fine!

[mgogoulos]

Forgot to include the new fixtures file..

[erjohnso]

Great, thank you very much @mgogoulos! One last request, could you please rebase and squash into a single commit? See, https://libcloud.readthedocs.org/en/latest/development.html#squash-the-commits-and-generate-the-patch. We don't need the patch, but see the two Notes in that section for rebasing/squashing if you've never done it.

[mgogoulos]

Should be fine now, after tests complete!

[erjohnso]

Thank you very much @mgogoulos - merging now.