rhbz1857749: uprobes-inode regression in sdt semaphore setting

rhbz1857749: uprobes-inode regression in sdt semaphore setting

Previous code neglected to set sdt.h semaphores for more than the
first process systemtap happened to encounter.  This was from a
mistaken understanding of what it meant for stapiu_change_plus() to be
called with the same inode/consumer combination.  Even though uprobes
are automatically shared, each new process still needs its perfctr and
sdt-semaphores individually set, so we do that now (as before the
rework of this code).  Mechanized testing incoming shortly.