drop_delete with saved token fails in cloud

Encountered unexpected behavior with running the following code:

```
#token_drop <- drop_auth() #initialized in first run
#saveRDS(token_drop, "/path/to/droptoken.rds")
token_drop <- readRDS("/path/to/droptoken.rds")
drop_acc(dtoken=token_drop, verbose = TRUE)
#get a list of items in the directory
data <- drop_dir("/list/items", dtoken = token_drop)
#get the first item on the drop box list
drop_get(as.character(data[1,1]),local_file = "dt_items.Rdata" ,dtoken = token_drop, overwrite = TRUE)
#load the data.table to environment
load(paste0(getwd(),"/dt_items.Rdata"))
#remove the local file
file.remove(paste0(getwd(),"/dt_items.Rdata"))
#remove the dropbox file
drop_delete(as.character(data[1,1]), dtoken = token_drop)
```

The **drop_dir** and **drop_get** run without starting the oauth flow **Expected**.

**drop_delete** always causes browser to open a window for oauth flow. **Unexpected**.
Shouldn't this follow suit with drop_get and not start the oauth because token is provided?

Happens with dev and cran version. EDIT:And added bonus is that I run R in Google Cloud

```

> Platform: x86_64-pc-linux-gnu (64-bit)
> Running under: Debian GNU/Linux 8 (jessie)
>
> locale:
> [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C LC_TIME=en_US.UTF-8
> [4] LC_COLLATE=en_US.UTF-8 LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
> [7] LC_PAPER=en_US.UTF-8 LC_NAME=C LC_ADDRESS=C
> [10] LC_TELEPHONE=C LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
>
> other attached packages:
> [1] dplyr_0.4.3 rdrop2_0.7 data.table_1.9.6 bigrquery_0.1.0.9000
> [5] httr_1.1.0.9000 PKI_0.1-3 base64enc_0.1-3
>
> loaded via a namespace (and not attached):
> [1] Rcpp_0.12.4 digest_0.6.9 withr_1.0.1 assertthat_0.1 chron_2.3-47 R6_2.1.2
> [7] jsonlite_0.9.19 DBI_0.4 git2r_0.13.1 magrittr_1.5 lazyeval_0.1.10 curl_0.9.7
> [13] devtools_1.11.1 tools_3.2.3 httpuv_1.3.3 parallel_3.2.3 memoise_1.0.0 openssl_0.9.2
> > library(devtools)
> > session_info()
> Session info ----------------------------------------------------------------------------------------------
> setting value
> version R version 3.2.3 (2015-12-10)
> system x86_64, linux-gnu
> ui RStudio (0.99.491)
> language (EN)
> collate en_US.UTF-8
> tz
> date 2016-05-02
>
> Packages --------------------------------------------------------------------------------------------------
> package * version date source
> assertthat 0.1 2013-12-06 CRAN (R 3.2.3)
> base64enc * 0.1-3 2015-07-28 CRAN (R 3.2.3)
> bigrquery * 0.1.0.9000 2016-02-27 Github (rstats-db/bigrquery@2866909)
> chron 2.3-47 2015-06-24 CRAN (R 3.2.3)
> curl 0.9.7 2016-04-10 CRAN (R 3.2.3)
> data.table * 1.9.6 2015-09-19 CRAN (R 3.2.3)
> DBI 0.4 2016-05-02 CRAN (R 3.2.3)
> devtools * 1.11.1 2016-04-21 CRAN (R 3.2.3)
> digest 0.6.9 2016-01-08 CRAN (R 3.1.1)
> dplyr * 0.4.3 2015-09-01 CRAN (R 3.2.3)
> git2r 0.13.1 2015-12-10 CRAN (R 3.2.3)
> httpuv 1.3.3 2015-08-04 CRAN (R 3.2.3)
> httr * 1.1.0.9000 2016-04-28 Github (hadley/httr@7261a52)
> jsonlite 0.9.19 2015-11-28 CRAN (R 3.2.3)
> lazyeval 0.1.10 2015-01-02 CRAN (R 3.2.3)
> magrittr 1.5 2014-11-22 CRAN (R 3.1.1)
> memoise 1.0.0 2016-01-29 CRAN (R 3.2.3)
> openssl 0.9.2 2016-02-26 CRAN (R 3.2.3)
> PKI * 0.1-3 2015-07-28 CRAN (R 3.2.3)
> R6 2.1.2 2016-01-26 CRAN (R 3.2.3)
> Rcpp 0.12.4 2016-03-26 CRAN (R 3.2.3)
> rdrop2 * 0.7 2016-05-02 Github (karthik/rdrop2@15e59ef)
> withr 1.0.1 2016-02-04 CRAN (R 3.2.3)
```