[ci] 'cargo-tarpaulin:v0.18.0' does not accept '--all-targets' anymore

[woshilapin]

There was a change of version of cargo-tarpaulin on the 28th of June. The new version doesn't accept --all-targets anymore so our CI fails. This PR should fix it.

[woshilapin]

Removing --all-targets for version 0.18.0 seems to bring some other problems. Instead, I propose we force version 0.16.0 which was working just fine.

[woshilapin]

The version 0.18.0 of tarpaulin seems to need some OS functionality named ASLR. The problem is that this kind of functionality is disabled in most CI runners of the market (Github, Gitlab, Travis at least). There might be ways to get over that problem, but the simplest solution is to stick to 0.16.0 for now.

More datails can be found in the documentation about running cargo-tarpaulin with Docker. There is also a few issues with some valuable information in them:

• fails on travis with ASLR disable failed: EPERM xd009642/tarpaulin#77
• Get error ASLR disable failed: EPERM: Operation not permitted when executing cargo tarpaulin -v xd009642/tarpaulin#146
• ASLR disable failed: EPERM: Operation not permitted xd009642/tarpaulin#406