[pve-devel] fix cyclic dependency between pve-manager and pve-guest-common

[Thomas Lamprecht]

We used PVE::VZDump from inside pve-guest-common for logging and a
slightly wrapped PVE::Tools::run_command.

Move the log helper to the base class and inline the run_command also
there, which then allows to remove the cyclic dependency.
In a second patch reduce code duplication and let PVE::VZDump use the
base plugins log method. I though about adding this log method to
pve-common (SafeSyslog) but with those two as single user this felt
not waranted currently.

The guest-common patch works on its own but the manager one needs the
other to work.

My "vzdump: allow all defined log levels" series needs to be respinned
after this change.

cheers,
Thomas