It is generally not possible to install two versions of the same package. This usually results in unresolvable file conflicts, although there are rare cases in which you can have multiple versions of a package installed without conflict (e.g., the kernel
package).
It is possible to create a "fake" package that fulfills the missing dependency, although doing so indicates that something on your system is fundamentally broken (typically, someone has installed something that wasn't really intended for use on the particular distribution you're using). You would need to create a spec file with a Provides:
line matching your dependency, along the lines of:
Provides: mysql = 5.5.22
Once upon a time I wrote a tool called fakeprovide that helps out with this sort of thing...if nothing else it might give you a template spec file to work with.
You could also grab the source RPM for collectd
and rebuild it to be compatible with the version of MySQL
installed on your system.