Fixes #4904: Move r32734 to v1.8 branch (OMPI: btl openib: fix detection)

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r32734 [[BR]]
OMPI: btl openib: fix detection of max registarable memory
    
Deal with the case when mlx4 module is loaded but device
is not present

cmr=v1.8.3:reviewer=miked
Fixes #4906: Move r32736 to v1.8 branch (BTL/OPENIB: set "max_lmc" param to)

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r32736 [[BR]]
BTL/OPENIB: set "max_lmc" param to be "1" and not "all available values" by default.

    cmr=v1.8.3:reviewer=miked