recover_mnesia_SUITE: increase reliability
recover_mnesia_SUITE: increase reliability

The test kills a minority of nodes. However, it could kill a majority of the key-space.
Increasing the number of nodes should reduce the likelihood for timeouts.

caijieming-baidu/scalaris,jvf/scalaris,jvf/scalaris,caijieming-baidu/scalaris,jvf/scalaris,scalaris-team/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,jvf/scalaris,scalaris-team/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,jvf/scalaris,jvf/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,jvf/scalaris,caijieming-baidu/scalaris