Remove goma_ctl support from mojob.

I ran into this because mojob didn't detect my GOMA_DIR
being set (which I set eons ago because that's what goma
expects).  I fixed mojob to support GOMA_DIR but then I
noticed that running goma_ctl.py before running ninja
more than doubled the null-build time (which is one of the
features of ninja).

I also noticed that the goma_ctl output more than doubled
ninja's null output, so I wrote some code to only display
the output on failure...

But since gn-based ninja build already knows how to respect
use_goma and goma's gcc wrapper already knows how to auto
start itself, the goma_ctl check is really unneeded.

Once I removed the goma_ctl output I realized mojob's
"i'm building out/Debug" was also redundant with ninja's
own ouput.  So I removed that too.

BUG=
R=viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/753753003