Travis: Update from bionic to focal and from xenial to bionic

[stefanberger]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 2698

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1607 unchanged lines in 72 files lost coverage.
• Overall coverage decreased (-0.3%) to 77.124%

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Files with Coverage Reduction	New Missed Lines	%
src/tpm12/tpm_platform.c	1	19.35%
src/tpm12/tpm_secret.c	1	80.95%
src/tpm2/BackwardsCompatibilityObject.c	1	0%
src/tpm2/ContextCommands.c	1	90.85%
src/tpm2/crypto/openssl/CryptPrimeSieve.c	1	97.48%
src/tpm2/CryptSelfTest.c	1	97.37%
src/tpm2/Entity.c	1	88.13%
src/tpm2/EphemeralCommands.c	1	75.56%
src/tpm2/IntegrityCommands.c	1	79.82%
src/tpm2/ManagementCommands.c	1	35.71%

Totals
Change from base Build 2696:	-0.3%
Covered Lines:	33875
Relevant Lines:	43923

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💛 - Coveralls