An attempt to run tests on rust 1.41

[alekseysidorov]

No description provided.

[coveralls]

Coverage remained the same at 84.928% when pulling 1710a3f on alekseysidorov:test_rust_1.41 into 3c1d023 on exonum:master.

[vitvakatu]

This configuration forces dynamic linkage of librocksdb:

⇒  otool -L target/debug/libjava_bindings.dylib
target/debug/libjava_bindings.dylib:
	@rpath/libjava_bindings.dylib (compatibility version 0.0.0, current version 0.0.0)
	@rpath/libstd-861a2dddfff9db3f.dylib (compatibility version 0.0.0, current version 0.0.0)
	<....>
	/usr/local/opt/rocksdb/lib/librocksdb.6.5.dylib (compatibility version 0.0.0, current version 0.0.0)
	<....>

While possible, it requires to distribute dynamic rocksdb library somehow. Some considerations are collected in https://jira.bf.local/browse/ECR-3405

Static linkage does not work on both platforms, as rust-lang/rust#64340 is not fixed.

[vitvakatu]

Judging by Travis history, this build is slower by 5-6 minutes by each job, i.e. 15-18 minutes for the whole build. 😕