Change jemalloc detection

[fmbiete]

Simplify jemalloc detection for cases where is not in standard locations or we have multiple versions available in the system. pmap is always the source of truth for what libraries are being used.

[it-percona]

All committers have signed the CLA.

[fmbiete]

This would also solve: PT-1628

[svetasmirnova]

We cannot repeat PT-1628 anymore. This contribution does not test cases, demonstrating the issue and its resolution, so rejecting it. If you can update it to the current version, put the fix into the proper place, and add test cases, feel free to re-open it.