OSHMEM: various fixes

1. fix in oshmem scoll component: basic algorithms should
   call basic collectives since their implementation
   incompatible with others (fca, hcoll).

2. Set OPAL_EVLOOP_ONCE flag ON for libevent in the case 
   of yoda smpl. Otherwise there is possible deadlock in 
   atomic_basic_lock call

fixed by Val, Igor, reviewed by Miked

cmr=v1.7.5:reviewer=ompi-rm1.7