CipherTest: in ASN1 encoding for GCM, no value for tag size means 12

(cherry picked from commit d3204de83ff89519bd2f7c5b3260e508936d58d2)

Bug: 26231099
Bug: 26234568
Bug: 29876633
Change-Id: I7d194de82506cf3da4dbb0b2cc67b72f3623abe7
1 file changed