module: Unify the return value type of try_module_get

The prototypes of try_module_get are different with different macro.
When enable module and module unload, it returns bool, but others not.
Make the return type for try_module_get consistent across all module
config options.

Signed-off-by: Gao Feng <fgao@ikuai8.com>
[jeyu: slightly amended changelog to make it clearer]
Signed-off-by: Jessica Yu <jeyu@redhat.com>