Ensure conda installer is not used for non-conda environments

[DonJayamanne]

Fixes #969

[codecov]

Codecov Report

Merging #1065 into master will not change coverage.
The diff coverage is 50%.

@@           Coverage Diff           @@
##           master    #1065   +/-   ##
=======================================
  Coverage   64.04%   64.04%           
=======================================
  Files         260      260           
  Lines       12010    12010           
  Branches     2133     2133           
=======================================
  Hits         7692     7692           
  Misses       4309     4309           
  Partials        9        9

Impacted Files	Coverage Δ
src/client/common/installer/condaInstaller.ts	55.26% <50%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update dc78b31...6aabfc4. Read the comment docs.