fix_randn_problem_with_covariance_matrix

[AtsushiSakai]

try to fix randn problem with covariance matrix #236

[coveralls]

Pull Request Test Coverage Report for Build 1034

• 96 of 96 (100.0%) changed or added relevant lines in 5 files are covered.
• 18 unchanged lines in 6 files lost coverage.
• Overall coverage remained the same at 90.275%

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Files with Coverage Reduction	New Missed Lines	%
PathPlanning/ClosedLoopRRTStar/pure_pursuit.py	1	96.12%
PathPlanning/ClosedLoopRRTStar/closed_loop_rrt_star_car.py	2	70.54%
PathPlanning/RRTStarReedsShepp/rrt_star_reeds_shepp.py	2	80.42%
PathPlanning/ReedsSheppPath/reeds_shepp_path_planning.py	3	91.14%
ArmNavigation/n_joint_arm_to_point_control/n_joint_arm_to_point_control.py	4	93.59%
PathPlanning/BatchInformedRRTStar/batch_informed_rrtstar.py	6	81.41%

Totals
Change from base Build 1030:	0.0%
Covered Lines:	6702
Relevant Lines:	7424

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💛 - Coveralls