Fix trt installation in CI (#18609)

Fix trt installation in CI (#18609)

Summary:
caffe2_py2_cuda9_0_cudnn7_ubuntu16_04_build is failing
```
...
Mar 29 04:44:46 Need to get 174 MB of archives.
Mar 29 04:44:46 After this operation, 576 MB of additional disk space will be used.
Mar 29 04:44:46 Do you want to continue? [Y/n] Abort.
Exited with code 1
...
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18609

Differential Revision: D14694990

Pulled By: bddppq

fbshipit-source-id: 260446a8650f660a2baf123a3f17efdf0a8d6c64