Fix ssl problem in bioc_install command

[roi-meir]

Problem

Currently, the tests fail at the first bioc_install command because of SSL error

For example:

package 'BiocManager' successfully unpacked and MD5 sums checked
The downloaded binary packages are in
	C:\Users\appveyor\AppData\Local\Temp\1\Rtmpai2tJU\downloaded_packages
Error: Bioconductor version cannot be validated; no internet connection?  See
  #troubleshooting section in vignette
In addition: Warning messages:
1: In file(con, "r") :
  URL 'https://bioconductor.org/config.yaml': status was 'SSL connect error'
2: In file(con, "r") :
  URL 'https://bioconductor.org/config.yaml': status was 'SSL connect error'
Execution halted
Command exited with code 1
7z a failure.zip *.Rcheck\*
7-Zip 19.00 (x64) : Copyright (c) 1999-2018 Igor Pavlov : 2019-02-21

Fix

Set R_LIBCURL_SSL_REVOKE_BEST_EFFORT to TRUE (see https://stat.ethz.ch/R-manual/R-devel/library/utils/html/download.file.html for details)
and set curl backend to openssl using CURL_SSL_BACKEND variable.

[roi-meir]

There is another error while installing the package but this fix resolves the SSL issue

 checking whether package 'harmony' can be installed ... ERROR
Installation failed.
See 'C:/projects/harmony-u35gr/harmony.Rcheck/00install.out' for details.
* DONE
Status: 1 ERROR
See
  'C:/projects/harmony-u35gr/harmony.Rcheck/00check.log'
for details.
Command exited with code 1
7z a failure.zip *.Rcheck\*