Wrapping ssh calls into subprocesses

Eventlet does not work properly with Paramiko when several connections
are opened concurrently (see bug #1212341). The fix moves ssh calls
from main code to subprocess to avoid the issue.

Also changed:
 * added timeout to all remote operations
 * old SSH utilities were moved from remote.py to integration tests,
   because new ones can not be utilized there

Fixes: bug #1212341

Change-Id: Ib89af3a3bbcb587af46dad3431d512a21d1ba826
Merge "Wrapping ssh calls into subprocesses"