Occasional testUnit3 failure

[Frank Dellaert]

With output:

not equal:
expected[2.6798178; -1.63956723];
actual[2.79128001; -1.70776209];
/home/jenkins/jenkins_home/jobs/gtsam-ubuntu-pullrequest/workspace/BUILD_OPT/Release/MKL_OPT/MKL OFF/ROT_OPT/Rot3/TBB_OPT/TBB ON/gtsam/geometry/tests/testUnit3.cpp:282: Failure: "assert_equal(v12, actual_v12, 1e-3)" 
Not equal:
expected:
:[0.161959219, 0.629138461, 0.760232865]';
actual:
:[0.0934753343, 0.716423475, 0.691375272]';
/home/jenkins/jenkins_home/jobs/gtsam-ubuntu-pullrequest/workspace/BUILD_OPT/Release/MKL_OPT/MKL OFF/ROT_OPT/Rot3/TBB_OPT/TBB ON/gtsam/geometry/tests/testUnit3.cpp:284: Failure: "assert_equal(s2, actual_s2, 1e-3)" 
There were 2 failures

Assigning to @lvzhaoyang as we discussed him taking a look at Unit3 retract, anyway, using manopt inspiration...