samba4: remove double quotes for renice

samba4: remove double quotes for renice

The double quote thells the shell that the list returned from `pidof` is a
single argument, therefore, `renice` will cry about a malformed input.
With this commit, `renice` will be applied correctly to all the returned PIDs
from `pidof`.

The output of `renice` for the quoted list is as follows:
`renice: invalid number '6592 6587 6586 6574'`
`renice` does not show and does apply the nice value if the list is unquoted.

Signed-off-by: Oever González <notengobattery@gmail.com>
Signed-off-by: Jan Pavlinec <jan.pavlinec@nic.cz>