Don't search global store when DOTNET_MULTILEVEL_LOOKUP is disabled (dotnet/core...

Don't search global store when DOTNET_MULTILEVEL_LOOKUP is disabled (dotnet/core-setup#3326)

The global store location is being searched when the DOTNET_MULTILEVEL_LOOKUP environment variable is zero (disabled). DOTNET_MULTILEVEL_LOOKUP controls whether the global locations are used when looking for the shared framework (C:\Program Files\dotnet\shared), and the change here is to also have DOTNET_MULTILEVEL_LOOKUP control whether the store global location (C:\Program Files\dotnet\store) is searched.

Commit migrated from https://github.com/dotnet/core-setup/commit/88da334986d5f560c98248c2cfff6e5816cdde7a