ShellEscape(string) doesn't escape a string with spaces like "arg1
arg2". However, when we want to escape a string to use it as an
argument, then strings with spaces should be escaped.
For example,
"command " + ShellEscapeIncludingSpaces("a b")
becomes "command 'a b'" so that "command" will get "a b" as a single
argument.
Bug: 182092664
Test: Added tests to escape_test.go
Change-Id: I8f88c18bc4f9f7aacfe9e701b8f0876dd8b9a8c3
ddb5ed7e1f