[distcc] fix Issue #145. Allow -j (jobs) param to set number slots when used in zeroconf mode.

[Eric Fontaine]

To fix issue https://github.com/distcc/distcc/issues/145 I submitted the 
following pull request: https://github.com/distcc/distcc/pull/187

"If server is started in zeroconf mode, the previous behavior was that 
the number of slots for any server was hardcoded to 4 * number of cpus. 
This made zeroconf impracticle when different hosts had different core 
counts.
This commit allows distccd to be invoked in zeroconf mode with the -j 
parameter to specify total slots for the particular server being 
invoked.
If no -j specified, then this host will publish its total number of 
slots to be 2 * number of cores + 2. (Note: this is the same behavior as 
when invoking a non-zerconf server without specifying -j.)
To maintain backward compatibily, if a distccd zeroconf server doesn't 
publish a value for slots, then it will be assigned a default total 
slots equal to the previous behavior of 4 * number of cores.
Note that the meaning of 'slots' in the code now always refers to the 
number of slots per host. (The previous interepration of 'slots' was 
inconsistent, because sometimes it meant the number of slots per core.)"

I've tested my fixed zeroconf mode on my home network which has one 
computer with 8 cores and one with 2 cores, and it seems to be working.  
I had commented on your github issue page a couple months ago but no 
response, but no response.  Anyway, I was wanting for a solution since I 
have a bunch of machines with different core counts, and sometimes I 
don't have them all powered on, and I didn't want to have to change 
configuration based on what computers I had powered on at the moment.

Anyway, I think others might also want this so please consider this pull 
request.  I tried to keep the prior behavior as much as possible and 
stick with same code style, but let me know if I should change anything.

-Eric Fontaine