erasure-code: test jerasure SSE optimized plugins selection

erasure-code: test jerasure SSE optimized plugins selection

Test the selection of the plugin depending on the CPU features. The
prefix of the plugin is "jerasure" by default (jerasure_generic,
jerasure_sse3, jerasure_sse4) and can be modified with the
"jerasure-name" parameter. A test plugin is created for each
variant (test_jerasure_generic, test_jerasure_sse3, test_jerasure_sse4).
The flags set by ceph_probe are modified by the test to check if the
expected plugin suffix is appended.

Signed-off-by: Loic Dachary <loic@dachary.org>