Revert "Fix conflcit lib/msf/util/exe.rb"

This reverts commit 3996557ec61a6eeefaa3448480012205b8825374, reversing
changes made to 62102dd1f913a0ac43f4f8359999a571e09c11d9.

@wchen-r7 , please verify. This was causing build failures:

https://travis-ci.org/rapid7/metasploit-framework/builds/13816889

It looks like there were a whole bunch of changes that weren't intended.

Reverting this commit resolves the rspec tests, but now it's difficult to tell what was lost in the PRs you landed after f5d1d8eacee7e11255e02ae38c4780cf4f8a642a#diff-0f5729034d8b0b321e738f2fc047854f .

Specifically, PR #2577 and #2544. Those may have to be redone.