profiler: Fix error handling

[javierhonduco]

The err variable was clobbered so we were reading the wrong value

Test Plan

--- a/pkg/profiler/cpu/bpf/maps/maps.go
+++ b/pkg/profiler/cpu/bpf/maps/maps.go
@@ -1140,6 +1140,7 @@ func (m *Maps) AddUnwindTableForProcess(pid int, executableMappings unwind.Execu
        // is challenging if the process name contains spaces, etc).
        //  - PIDs can be recycled.

+       return fmt.Errorf("le error")
        m.mutex.Lock()
        defer m.mutex.Unlock()

Before:

msg="failed to add unwind table" pid=18846 err=null

After:

msg="failed to add unwind table" pid=18846 err="le err"

[javierhonduco]

Fixes #2314