Avoid internationalization problems (work around)

Tests assume dollars (and . as decimal separator?)
my default LANG=sv_SE.UTF-8
setting it to C works as a workaround but this needs some thought...

First failed test case for iap-sample-app
> ant clean test

Testcase: canShowProductInListView took 0,087 sec
	FAILED
null expected:<red sock - $[1.00]> but was:<red sock - $[,00 kr]>
junit.framework.AssertionFailedError: null expected:<red sock - $[1.00]> but was:<red sock - $[,00 kr]>
	at tv.ouya.sample.IapSampleActivityTest.canShowProductInListView(IapSampleActivityTest.java:94)
	at com.xtremelabs.robolectric.RobolectricTestRunner$1.evaluate(RobolectricTestRunner.java:288)