Add option to turn off command logging to GetCommandOutput
Add option to turn off command logging to GetCommandOutput

The command logging performed by GetCommandOutput can be distracting
and unwelcome. This patch adds a switch allowing the command output to
be muted as needed.

Signed-off-by: Hrvoje Ribicic <be5828fca31f89218048bec4189e30a581aa65da@google.com>
Reviewed-by: Petr Pudlak <9d19625f8ee825a2c398462ed335cbcf98f79c32@google.com>

ganeti/ganeti,grnet/snf-ganeti,ganeti/ganeti,ganeti-github-testing/ganeti-test-1,mbakke/ganeti,apyrgio/ganeti,apyrgio/ganeti,onponomarev/ganeti,grnet/snf-ganeti,dimara/ganeti,andir/ganeti,leshchevds/ganeti,yiannist/ganeti,andir/ganeti,dimara/ganeti,bitemyapp/ganeti,mbakke/ganeti,onponomarev/ganeti,yiannist/ganeti,ganeti/ganeti,bitemyapp/ganeti,leshchevds/ganeti,mbakke/ganeti,leshchevds/ganeti,andir/ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1