Allow other period notations in free-busy report verifier

[tobiasfriedrich]

Test 1 in suite free-busy reports of file scripts/tests/CalDAV/availability.xml uses a dataString verifier, in which the existence of the string FREEBUSY;FBTYPE=BUSY:$now.year.1:0104T170000Z/PT1H is checked.

However, as the same period can also be expressed as period-explicit (RFC 5545, section 3.3.9), this should be considered appropriately by the test, so that a string FREEBUSY;FBTYPE=BUSY:$now.year.1:0104T170000Z/$now.year.1:0104T180000Z wouldn't fail the test either.