use of deprecated method inotify::Inotify::add_watch

[olafhering]

After upgrading from 4ccc639 to 59d55a8, build starts to fail:

   Compiling nitro-cli v1.2.2 (/home/abuild/rpmbuild/BUILD/aws-nitro-enclaves-cli-1.2.2~git79.59d55a8)
error: use of deprecated method `inotify::Inotify::add_watch`: use `Inotify.watches().add()` instead
  --> src/enclave_proc/socket.rs:89:14
   |
89 |             .add_watch(
   |              ^^^^^^^^^
   |
note: the lint level is defined here
  --> src/enclave_proc/socket.rs:4:9
   |
4  | #![deny(warnings)]
   |         ^^^^^^^^
   = note: `#[deny(deprecated)]` implied by `#[deny(warnings)]`

error: could not compile `nitro-cli` (lib) due to previous error

The same appears in #547. Full log:
log.Cloud:Tools.aws-nitro-enclaves-cli.openSUSE_Tumbleweed.x86_64.txt

[olafhering]

This was apparently fixed by #597