libprocessgroup: Use uid_t consistently for UIDs

Found with -Wsign-conversion.

Test: m
Change-Id: I302ce3c2ffdd533fe45e98c5c7edbb442db46ae4
diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index 3209adf..42d415a 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -747,7 +747,7 @@
     return CgroupGetAttributePathForTask(attr_name, tid, path);
 }
 
-bool isProfileValidForProcess(const std::string& profile_name, int uid, int pid) {
+bool isProfileValidForProcess(const std::string& profile_name, uid_t uid, int pid) {
     const TaskProfile* tp = TaskProfiles::GetInstance().GetProfile(profile_name);
 
     if (tp == nullptr) {