Add flag to grant permissions when running tests.

This change automatically adds -g to all adb install commands
for runtest. It also allows users to:
1) Specify '-k' as a command line arg to avoid granting permissions.
2) Declare a test suite as 'requiring permissions' within test_defs

Also fixes a potential bug where continuous="false" would translate
to True in the python code.

Bug: 21327566
Change-Id: I62d14e8106174861397b3fd8caa3e567e3538713
5 files changed