sepolicy-analyze: Change booleans command to be more test-friendly.

Instead of displaying the boolean count, display a list of booleans
defined in the policy, if any.  This makes sepolicy-analyze booleans
consistent with sepolicy-analyze permissive and allows automated tests
to simply check whether there was any output at all.

Change-Id: I221b60d94e6e7f6d80399bf0833887af3747fe83
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>