For saya (arm) use arm gitbuilder for ceph sha1.
For saya (arm) use arm gitbuilder for ceph sha1.

Since the arm gitbuilder (even using a ton of nodes for distcc) is
much slower than x86 lets grab the sha1 from its own gitbuilder
when machine_type is saya rather than the x86 one.

Signed-off-by: Sandon Van Ness <a38d61b815b8053a15c463c80449b5c080334ec7@inktank.com>

michaelsevilla/teuthology,ivotron/teuthology,SUSE/teuthology,SUSE/teuthology,tchaikov/teuthology,michaelsevilla/teuthology,ceph/teuthology,ktdreyer/teuthology,dreamhost/teuthology,robbat2/teuthology,zhouyuan/teuthology,dreamhost/teuthology,yghannam/teuthology,caibo2014/teuthology,yghannam/teuthology,dmick/teuthology,ivotron/teuthology,t-miyamae/teuthology,ceph/teuthology,dmick/teuthology,tchaikov/teuthology,caibo2014/teuthology,dmick/teuthology,SUSE/teuthology,zhouyuan/teuthology,t-miyamae/teuthology,ktdreyer/teuthology,robbat2/teuthology