Don't match editor backup files in environment

The current glob match for environment files can source editor backup
files (foo.bash~) which will override the real changes you have made.

Other parts use the regex to avoid matching such files, so do
the same for environment file matching.  Note this has to match "."
unlike the other regex, as most env files are "foo.bash"

Port to dib-utils of: I934486b3ff5884063d29c6d9b66fd9b11140464c
Change-Id: I11c030e8556d89c240e36233b249f0c1d9f80908