Removes security_groups from _create_server_volume_heat signature

Closes-Bug: #1254607

Change-Id: I22b6af351dd3a371443f432c01785c706eff8397
Removes unused import statements

Updates tox.ini to remove suppressed F401 standard.

Updates the code files containing unused import statements

Change-Id: Ib44bd1509fdb17f457a205f9e62caf85cebee830
Closes-Bug: #1257267
Remove 'mount_point' from guestagent RPC API

'mount_point' is used inconsistently across guestagent code.
Sometimes its value is taken from parameters of RPC call
and sometimes from CONF.
This patch makes this value being taken from existing my.cnf.
'mount_point' paramenter is removed from all trove-*.conf
files.

Blueprint remove-mount-point-from-parameters-for-instance-prepare

Fixes bug 1248212

Change-Id: I2631f7b7cd0de9a13a20bd986b7f3fe8d363bf0e