btl/usnic: move btl_usnic_lock initialization

[lrbison]

Previously it was in component_init, but after
#12057 I noticed MPI finalize would find an uninitialized object and segfault. This change moves the initialization to component_open, so that component_close() can rely on the opal object initialization having been completed.

---

My reproducer on main was:

 mpirun -n 2 --mca pml cm  --mca pml_base_verbose 10 -- ./hello_world

which previously crashed with:

#0  opal_obj_run_destructors (object=0xffff86302dc8 <btl_usnic_lock>) at ../../../../opal/class/opal_object.h:470
#1  0x0000ffff862d87cc in usnic_component_close () at btl_usnic_component.c:215
#2  0x0000ffff8d7a042c in mca_base_component_close (component=0xffff86302788 <mca_btl_usnic_component>, output_id=-1) at mca_base_components_close.c:52
#3  0x0000ffff8d7a054c in mca_base_components_close (output_id=-1, components=0xffff8d845d20 <opal_btl_base_framework+80>, skip=0x0) at mca_base_components_close.c:89
#4  0x0000ffff8d7a04f0 in mca_base_framework_components_close (framework=0xffff8d845cd0 <opal_btl_base_framework>, skip=0x0) at mca_base_components_close.c:70
#5  0x0000ffff8d80293c in mca_btl_base_close () at base/btl_base_frame.c:231
#6  0x0000ffff8d7a23ec in mca_base_framework_close (framework=0xffff8d845cd0 <opal_btl_base_framework>) at mca_base_framework.c:252
#7  0x0000ffff8db7d7b8 in mca_bml_base_close () at base/bml_base_frame.c:130
#8  0x0000ffff8d7a23ec in mca_base_framework_close (framework=0xffff8dc45608 <ompi_bml_base_framework>) at mca_base_framework.c:252
#9  0x0000ffff8dadf754 in ompi_mpi_instance_finalize_common () at instance/instance.c:945
#10 0x0000ffff8dadf850 in ompi_mpi_instance_finalize (instance=0xffff8dc5a938 <ompi_mpi_instance_default>) at instance/instance.c:975
#11 0x0000ffff8dad1bfc in ompi_mpi_finalize () at runtime/ompi_mpi_finalize.c:294
#12 0x0000ffff8db1c480 in PMPI_Finalize () at finalize.c:52

(gdb) p btl_usnic_lock
$1 = {super = {obj_class = 0x0, obj_reference_count = 0}, m_lock = {__data = {__lock = 0, __count = 0, __owner = 0, __nusers = 0, __kind = 0, __spins = 0, __list = {__prev = 0x0, __next = 0x0}},
    __size = '\000' <repeats 47 times>, __align = 0}, m_lock_atomic = 0}

My reproducer is now fixed, however I wonder if this is the correct fix, since #12057 removed the static init, and now we only have this object initialization.

In particular I'm not familiar with enough with MPI_init_thread to know if multiple threads may try to init the object at the same time, nor do I have a usnic test system.

[devreal]

Not familiar with the usnic btl but it makes sense to always construct the lock since it's always destroyed unconditionally.

[jsquyres]

@lrbison Many thanks for this. I did not realize that #12057 touched usnic. I'll review this shortly.

[jsquyres]

Thanks for submitting this fix!