ref: codecov#184
continuous from: ada583b

codecov#180 makes `find` command change to run through
`execFileSync()`. However, it always returns empty result because of
the quote has over-included as the filename of search condition. So
removed quotes from generated conditions.

In addition, removing brackets from find arguments (a4cc565) has
affected to the result of finding coverage files. This commit reverts
brackets to get back the original search condition too.

Previously quotes and escaped-brackets are required to run command on
the shell environment, but no longer need them because of using
`execFileSync()` that is disabled shell environment by default.