Always print instrumentation time in US locale

[li-wjohnson]

In instrumentation runners, instead of using the default locale, always print the "Time: " output in US locale. This fixes an issue where changing the device locale affects the format of the line and causes the instrumentation output parser in ddmlib to be unable to parse the time.

For example, if you set the device to use the Arabic locale, you currently get:

Time: ٣٫٦٤١