Bug#806812: Double messages upon disable

[積丹尼 Dan Jacobson]

After an install or an enable, the next disable will be good, but a
second and subsequent disable will have the repeated lines.

# systemctl disable haveged
Synchronizing state of haveged.service with SysV init with /lib/systemd/systemd-sysv-install...
Executing /lib/systemd/systemd-sysv-install disable haveged
insserv: warning: current start runlevel(s) (empty) of script `haveged' overrides LSB defaults (2 3 4 5).
insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6) of script `haveged' overrides LSB defaults (0 1 6).
# systemctl disable haveged
Synchronizing state of haveged.service with SysV init with /lib/systemd/systemd-sysv-install...
Executing /lib/systemd/systemd-sysv-install disable haveged
insserv: warning: current start runlevel(s) (empty) of script `haveged' overrides LSB defaults (2 3 4 5).
insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6) of script `haveged' overrides LSB defaults (0 1 6).
insserv: warning: current start runlevel(s) (empty) of script `haveged' overrides LSB defaults (2 3 4 5).
insserv: warning: current stop runlevel(s) (0 1 2 3 4 5 6) of script `haveged' overrides LSB defaults (0 1 6).