mkbootimg: use int for os_version and os_patch_level

The parse_int function attempts to interpret the string to detect
base, which leads to it assuming strings starting with 0 are base
8. This obviously fails for certain dates, so use int instead.

Bug: 27498078
Bug: 22914603
Change-Id: I50b1fb3d7876f2ec17d00649cc9a2d23af2aec2b
(cherry picked from commit 294eb9dac3)

mkbootimg/mkbootimg

@@ -102,12 +102,12 @@ def parse_int(x):
 def parse_os_version(x):
     match = re.search(r'^(\d{1,3})(?:\.(\d{1,3})(?:\.(\d{1,3}))?)?', x)
     if match:
-        a = parse_int(match.group(1))
+        a = int(match.group(1))
         b = c = 0
         if match.lastindex >= 2:
-            b = parse_int(match.group(2))
+            b = int(match.group(2))
         if match.lastindex == 3:
-            c = parse_int(match.group(3))
+            c = int(match.group(3))
         # 7 bits allocated for each field
         assert a < 128
         assert b < 128
@@ -118,8 +118,8 @@ def parse_os_version(x):
 def parse_os_patch_level(x):
     match = re.search(r'^(\d{4})-(\d{2})-(\d{2})', x)
     if match:
-        y = parse_int(match.group(1)) - 2000
-        m = parse_int(match.group(2))
+        y = int(match.group(1)) - 2000
+        m = int(match.group(2))
         # 7 bits allocated for the year, 4 bits for the month
         assert y >= 0 and y < 128
         assert m > 0 and m <= 12