ci: add testing under encfs #1775

Job	Run time
build-package	9m 2s
test-annex-more	19s
test-datalad (master)	1h 0m 32s
test-datalad (maint)	58m 13s
test-annex (normal, ubuntu-latest)	2m 35s
test-datalad (release)	58m 48s
test-annex (crippled-tmp, ubuntu-latest)	2m 30s
test-annex (crippled-home, ubuntu-latest)	2m 13s
test-annex (nfs-home, ubuntu-latest)	7m 7s
test-annex (custom-config1, ubuntu-latest)	2m 28s
test-annex (encfs-repo, ubuntu-latest)	5m 6s
	3h 28m 53s

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