libkmod-module: probe: return -EEXIST if told to do so

libkmod-module: probe: return -EEXIST if told to do so

Commit "af9572c lib/module: check initstate before inserting module"
removed the check for "we should return -EEXIST" and moved it back to
the start of the function. The problem with this is the following
scenario:

- We check if module is in kernel -> no
- We insert the dependencies
					<-- External program loads
					the module
- We check if module is in kernel -> yes
- We return 0, when we should return -EEXIST