different capability from different namespace required for prctl_set_mm_exe_file

[Tong Zhang]

Kernel Version: 4.18.5

Problem Description:

We discovered inconsistent check when using prctl_set_mm_exe_file(), which is 
used to setup exe file link.

It is required to have capable(CAP_SYS_RESOURCE) in prctl_set_mm().
while ns_capable(CAP_SYS_ADMIN) in prctl_set_mm_map().

There are two differences:
1)requiring capability from: user namespace, init namespace.
2)capability bit required is different


- Tong