Fix more leaks detected by ASAN

[dioni21]

Motivation and Context

Found some Leaks using ASAN compilation

Description

This commit fixes a bunch of missing free() calls created in a10d50f

How Has This Been Tested?

Build and run. Message is gone.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[dioni21]

@behlendorf could you please take a look at those test failures? I thought these changes were extremely simple, and the most intriguing is that only Ubuntu 18.04 failed.

[behlendorf]

Thanks. I agree, the failures look unrelated. We do have a couple false positives which can occur, let's see if we see these same failures again after updating this PR for the minor style issue.

[dioni21]

Good addition that STYLE check, BTW!

[codecov-io]

Codecov Report

Merging #10219 into master will increase coverage by 0.17%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #10219      +/-   ##
==========================================
+ Coverage   79.38%   79.55%   +0.17%     
==========================================
  Files         388      388              
  Lines      123392   123396       +4     
==========================================
+ Hits        97953    98171     +218     
+ Misses      25439    25225     -214     

Flag	Coverage Δ
#kernel	80.01% <ø> (+0.08%)	⬆️
#user	66.27% <100.00%> (+0.77%)	⬆️

Impacted Files	Coverage Δ
lib/libzfs/libzfs_dataset.c	76.48% <100.00%> (+0.04%)	⬆️
module/os/linux/spl/spl-zlib.c	55.35% <0.00%> (-28.58%)	⬇️
cmd/zvol_id/zvol_id_main.c	76.31% <0.00%> (-5.27%)	⬇️
module/zfs/dsl_synctask.c	92.40% <0.00%> (-2.54%)	⬇️
cmd/zed/agents/fmd_api.c	88.61% <0.00%> (-1.78%)	⬇️
module/os/linux/zfs/zfs_dir.c	82.91% <0.00%> (-0.69%)	⬇️
module/zfs/vdev_indirect.c	74.00% <0.00%> (-0.67%)	⬇️
cmd/zed/agents/zfs_mod.c	77.55% <0.00%> (-0.67%)	⬇️
cmd/zed/agents/zfs_diagnosis.c	78.42% <0.00%> (-0.30%)	⬇️
lib/libzfs/libzfs_mount.c	84.21% <0.00%> (-0.23%)	⬇️
... and 55 more

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