Bump docker images versions

[lukaszstolarczuk]

• update Fedora to 32 and Ubuntu to 20.04
• btw, set clang-format package to version 9.0 and run cppformat checks only on Ubuntu (because clang-format-9 on Fedora is not easily accessible)

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This change is 

[codecov]

Codecov Report

Merging #737 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #737      +/-   ##
==========================================
+ Coverage   95.02%   95.06%   +0.04%     
==========================================
  Files          42       42              
  Lines        4901     4901              
==========================================
+ Hits         4657     4659       +2     
+ Misses        244      242       -2     

Flag	Coverage Δ
#tests_clang_debug_cpp17	95.02% <ø> (-0.03%)	⬇️
#tests_gcc_debug	91.49% <ø> (+0.18%)	⬆️

Impacted Files	Coverage Δ
...ude/libpmemobj++/container/concurrent_hash_map.hpp	94.67% <0.00%> (+0.10%)	⬆️
...j++/container/detail/concurrent_skip_list_impl.hpp	97.56% <0.00%> (+0.14%)	⬆️

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[igchor]

Reviewed 6 of 6 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

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utils/docker/build.sh, line 87 at r1 (raw file):

# Only check cppformat on Ubuntu, since it has req. clang-format version
if [ "${OS}" == "ubuntu"]; then
	CHECK_CPP_STYLE=ON;

nit: not sure if it's a problem but with this if we cannot disable checking CPP_STYLE for ubuntu. Maybe we should check if this variable is explicitly OFF first?

[lukaszstolarczuk]

Reviewable status: 5 of 6 files reviewed, all discussions resolved (waiting on @igchor)

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utils/docker/build.sh, line 87 at r1 (raw file):

Previously, igchor (Igor Chorążewicz) wrote…

nit: not sure if it's a problem but with this if we cannot disable checking CPP_STYLE for ubuntu. Maybe we should check if this variable is explicitly OFF first?

Done.

[lukaszstolarczuk]

images' versions will be updated to LTS versions on all branches.

This PR will be probably merged into stable-1.9

[lukaszstolarczuk]

changes of this PR are covered already in #887 and we've changed approach for CHECK_CPP_STYLE (based on pmem/pmemkv@380cb14).