fix libicu package name is different on RHEL and Debian.

This commit fix the use of libicu package name.
So this will work on RHEL and Debian.

This commit have test coverage.

the method choose for implementation is described bellow:
It was created another variable specific for the libicu package name,
just like it was done to git_package_name.
This method has the advantage of being less prone to errors and sideefect
free.