Don't duplicate networks list on keypair import

In the Launch Instance modal, if the user clicks on the button to import
a keypair, the networks listed in the Networking tab get duplicated.

The import keypair button calls `workflow_init` which in turn calls
`generate_networklist_html` which appended the networks to the list, not
clearing it beforehand.

This makes sure both Selected Networks and Available Networks lists are
emptied before the networks are added.

Fixes bug 1170193

Change-Id: Icb750caa08673068c509af6c8df1ad57a2a30d93
Signed-off-by: Tomas Sedovic <tomas@sedovic.cz>
Fix translation error for missing default role

Fixes: bug #1175165
Change-Id: Ic3e19b47c5449740bec189f2c3a2e803d22fb5dc
Merge "Fix translation error for missing default role"
Merge "Don't duplicate networks list on keypair import"